PREVALENCE OF HYPERACTIVITY IN ELEMENTARY SCHOOL CHILDREN AS A FUNCTION OF SOCIAL SYSTEM DEFINERS

Amer. J . Orthopsychiat. 48(3), July I978

PREVALENCE OF HYPERACTIVITY IN ELEMENTARY SCHOOL CHILDREN AS A FUNCTION

OF SOCIAL SYSTEM DEFINERS

Nadine M. Lambed, Jonathan Sandoval, Dana Sassone

Department of Education, University of California, Berkeley

This study seeks to reconcile the widely varying estimates of prevalence of hyperactivity in children. Parents, teachers, and physicians were asked to identify hyperactive children in a sample of some 5000 elementary school children. Approximately five percent were considered hyperactive by at least one defining system; only one percent were considered hyperactive by all three definers. Prevalence rates were relatively constant from kindergarten through fifth grade.

t has been proposed that the number I of hyperactive children is growing rapidly each year. As an epidemiological statement, this implies that the incidence (the number of new cases each year) is increasing and therefore so is the prevalence (the number of existing cases). Such statements are usually tied to one of the following explanations: 1) etio- logical factors are changing (e.g., the amount of lead in the environment from the use of high octane gasoline is increasing, therefore hyperactivity is increasing ”) ; 2) social-political factors

are changing (e.g., drug companies are “pushing” drugs for children, therefore physicians give the diagnosis more often in order to justify the prescription 2e) ; 3 ) diagnostic sophistication is increasing and clinicians are just better able to rec- ognize the condition.80

The first explanation states that there actually are more hyperactive children. The second states that there are not more hyperactive children, but that more children are given the label. The third argument also posits that the number of hyperactive children is not greater,

Submitted to the Journal in May 1977.

446

LAMBERT, SANDOVAL AND SASSONE 447

but suggests that there were many more such children in the past who went un- recognized. Although all three points of view differ in basic assumptions about the meaning of hyperactivity, they all rely on the same type of prevalence study to provide evidence that “hyperactivity” is increasing.

It has been reported that the prevalence in school children of “hyperactivity,” “hyperkinesis,” or “MBD-hyperactivity” (minimal brain dysfunction-hyperactivity) ranges from 5 % to lO%.‘O What does this mean? From an epidemiological point of view, these figures are taken to mean that from five to ten out of any 100 school children have “hyperactivity.’’ The assumption has been made that hyperactivity is a medical condition or a disease, such as measles. The assumption also has been made that more than simple behaviors have been as- sessed, that an underlying condition, a syndrome, has been identified. Are these assumptions reasonable? Leaving aside the question of etiology, does the methodology used in prevalence studies meet the standards necessary for a medical epidemiological statement?

Defining for the purposes of estimating prevalence requires the presump- tion of a unitary entity that may be operationally defined. If one is investigating the prevalence of a specific disease entity, the task of definition is relatively simple. However, when one is investigating the prevalence of a problem that is defined by the absence of observable pathology and defined by behavioral characteristics that are reported s~bjec t ive ly ,~~ the task of definition is complex indeed. A first problem arises from the lack of observable pathology. When the lack of something (e.g., assessable brain damage) becomes

a criterion, there is a difficulty in de- ciding who does not meet the criterion. Are all children who are overactive but who do not have brain damage “hyperactive”? Obviously not, but the lack of brain damage is used as one criterion for the technical diagnosis of “hyperkinetic reaction of childhood.”

A second problem is that the report of the child’s behavior is made by those who contribute to the child’s environment, namely the parents and teachers. Because they are a part of the child’s environment, their attitudes and behaviors affect both the child’s behavior and their perception of the child’s behavior. Such subjective reports hardly can be comparable to laboratory methods used in medical diagnosis. Is a prevalence investigation of “hyperactivity” studying the prevalence of “a syndrome,” of “behavior,” or of a “report of behavior”? As will be seen, traditional studies have lumped all three together and presume to measure a syndrome, which we believe to be an un- justifiable practice. This does not mean that one cannot study the occurrence of: 1 ) a defined behavior, 2) the reports of behavior from various sources or 3) the diagnosis or labeling of hyperactivity. It does, however, mean that one must be careful to differentiate reports of behavior that are subjective from diag- noses given by professionals. In all cases, the report or diagnosis may be as much a reflection of the reporter or diagnos- tician as of the child. It therefore becomes incumbent on the prevalence investigator to specify the environment in which the behavior occurs and the source of the label or diagnosis along with the estimates.

We believe that a prevalence study of reported behaviors should look both at

448 PREVALENCE OF HYPERACTIVITY

the intra-child variables independent of the social system and at the social (ell- vironmental and attitudinal) factors that might affect the behavior and its labeling or diagnosis. The following sec- tion is a brief description of how the assumptions of each model (after Mer- cer 1 8 ) could be applied to the prevalence study of “hyperactivity.”

Models of Hyperactivity

A prevalence study from an organic, neurological, or metabolic deficit model (i .e. , a disease model) assumes that hyperactivity is inherent in the individual and that it can be diagnosed reliably. One model holds that a child’s behavior results from a dysfunction in the central nervous system which prevents normal self-control. Authors such as Wender 3o

maintain that medications, usually central nervous system stimulants, work to overcome the deficit and cause the child to function normally, just as insulin al- lows a diabetic to process sugar in the usual manner. People subscribing to this model often use the term hyperkinesis or minimal brain dysfunction when talking about hyperactive children. A variant of this model is Feingold’s hypothesis that hyperactive children react unfavor- ably to food chemicals and are, presum- ably, deficient in this regard. Another, by Morrison and Stewart,20 suggests the possibility of a genetic etiology. The neurological or metabolic models stress the biological condition of the child and pay less attention to the environment in which the child grows and develops.

Diagnosis of the deficit can occur either through medical tests or evidence of symptoms, or through a statistical procedure (e.g., deviations from the norm). Regardless of the methods of

diagnosis, the condition is considered solely an attribute of the individual. In other words, a report of behavior is considered evidence of a symptom equal to the finding on a medical laboratory test. Prevalence is determined by estimating the number of persons with a sig- nificant number of symptoms. Symptoms are not looked at in terms of environmental contingencies, but are assumed to be a by-product of the child’s internal state. They are a reflection of an internal condition and are not looked at as behaviors per se. Nearly all available prevalence studies look at “hyperactivity” from such a model. Some use a physician’s diagnosis; most use reports of behavior, taking into account neither the source of the report nor the context of the behavior. Others use a statistical definition assuming that a certain cutoff percentile point on a teacher rating procedure is evidence of “hyperactivity.”

A second model, one that incorpo- rates a sociological and anthropological perspective, is the social system model. Here, in contrast to the organic model, authors such as Conrad or Robin and Bosco 22 stress that hyperactive behavior is defined by the child’s social environment, including the child’s role in an institution (e.g., the family or the school). When a hyperactive child’s behavior is socially deviant and trans- gresses social system norms, the family or the school “create” the hyperactive child by labeling this behavior as such. In this model, very little emphasis is placed on the constitutional makeup of the child or on individual differences in children. “Hyperactivity” is regarded as an achieved status; it is a role played by those assigned the status. This status exists within, and is specific to, the social system in which it occurs. Preva-


lence rates, therefore, are specific to the type of social system: traditional prevalence rates, which ignore the environmental or sociocultural factors, are considered meaningless. One can achieve the status, that is, be labeled “hyperactive,” in one social system, such as the school, but not in others, such as the home or larger community. The status of hyperactivity is thought of, therefore, as a product of the social system and not a condition inherent in the child.

A third model, one on which our research program has been based, incor- porates both the social and the child- centered perspectives in a single inter- active system model. This model asserts that both individual differences in the organic and psychological makeup of the child and individual differences in the family and school environment of the child may contribute to whether or not a child is identified as “hyperactive.” Rather than viewing the social structure as the sole arbiter of hyperactive behavior, the multidimensional or interac- tive model posits a complex interaction between the child’s environment and his physical and psychological status. Chil- dren function on a continuum of physical-neurological capacity and develop on a continuum of supportive social environments.

It follows, then, that hyperactivity in children cannot be defined by a single behavioral dimension or a single defining system. A definitive diagnosis based on the etiology of the symptoms is not realistic at this time, and multiple rather than single treatment recommen- dations are desirable. We accept the assumption that the severity of the hyperactive behaviors may be related to factors in the child’s home and school environments, and that the flexibility of

these two critical environments affects the child’s prognosis.

Our prevalence study will offer a number of different definitions of hyperactivity based on information from several sources: home, school, and physician. We shall not produce one prevalence rate for hyperactivity, but several based on different defining systems. As much as possible, we shall provide environmental information along with figures attached to a particular definition. Before proceeding, however, it is informative to summarize what others have reported about the prevalence of hyperactivity.

Prevalence in the General School Population

Studies of the prevalence in the United States. The work of Huessy and his col- leagues 9* lo* l1. l2 is often cited in the literature as indicating that between ten and twenty percent of school children are “hyperkinetic.” The researchers had teachers of 500 second-grade school children in rural Vermont complete their own 21-item, five-point scale rating on the children. Anyone with a total score above the 80th percentile was considered a “problem” and “hyperkinetic.” l2

Thus, twenty percent is the prevalence rate often cited from this study, but the estimate cannot be accepted without question. By arbitrarily choosing the 80th percentile, the investigators picked the prevalence rate. Using a percentile cut-off on an unvalidated checklist is hardly an adequate method of diagnosis or identification. The authors claimed that the instrument was validated by the fact that some of the children in the top twenty percent included the children about whom teachers complained. That teachers complain about the same chil-


dren to whom they give high ratings should come as no surprise; however, behavior resulting in teacher complaint is hardly synonomous with “hyperkinetic syndrome.”

Huessy et a1 l2 further argued that the “hyperkinetic syndrome” is not as stable as many have assumed. They based their assertion on the fact that, when a similar rating was made on the same children two years later, only half of the top ten percent were still above the 80th percentile. But since there was no ex- ternal validation of the original “diagnosis,” it is hard to see how they justify such a conclusion. It would seem more reasonable to conclude that reports of children’s behavior change over time, without identifying a reason.

Wender 30 used a procedure in which the teacher rated whether or not speci- fied behaviors were a “problem.” He found that fifteen percent of a stratified sample of Montgomery County, Mary- land, children in first through sixth grades had teacher-reported problems of restlessness, and 22 % had problems of attention span. Wender concluded that . . . one-fifth to one-tenth of grade school children had problems considered to be manifestations of MBD (minimal brain dysfunction) to some (perhaps minor) degree. (p. 60 1

Werner et a1 31 used behavior check- lists and reports from parents and teachers to indicate the presence of hyperkinetic symptoms (hyperactive, dis- tractible, and irritable) in 750 Kauai children followed from before birth. They found that 8.79% of the boys and 3.2% of the girls (5.9% total) evi- denced symptoms at ten years of age.

Stewart et a lZs found that four percent of 47 first-grade children in St.

Louis grade schools who had been sta- tistically selected to be controls had been “diagnosed hyperactive.” No definition of the method used to conclude that the children were “diagnosed hyperactive” was provided, however. Furthermore, the four percent figure was a statistical extrapolation based on a hypothesized boy-girl ratio. Despite these methodolo- gical difficulties, Wender so reported that . . . Stewart et a1 . . . reported the prevalence of the “hyperactivity syndrome” to be approximately 4% in a population of St. Louis grade school children between the ages of five and eleven.

In a later study, Miller, Palkes and Stewartlo found that, in a population of 849 suburban St. Louis grade school children in grades third through sixth, 1.46% of the girls, 9.32% of the boys, and 5.53% overall were “diagnosed hyperactive.” The criteria for diagnosis were teacher report (yes or no format), the presence of overactive and distracti- ble behavior, and the presence of at least three out of 28 other “symptoms” such as “does not do homework,” “has changeable moods,” “seems to think he/ she is worthless.” No confirmation of the “diagnosis” was made, other than the “face” validity of the reported symptoms.

Studies of prevalence in Western Eu- rope. Prechtl and Stemmer,21 using a neurological sign (choreiform move- ments) and “behavioral problems” found the syndrome to be present in twenty percent of the boys and ten percent of the girls in Netherland schools. The symptoms were “severe” in five percent of the boys and one percent of the girls.

Bax3 and Rutter and Graham,24 using the criteria of 1) short attention

LAMBERT, SANDOVAL AND SASSONE 45 1

span and excess motor activity 2) which are observed by all familiar adults and 3) are not affected by presence of familiar adults, found a very low prevalence rate in the entire rural population of the Isle of Wight. Bax found no cases among 1200 five-year-olds, while Rut- ter found two out of 2199 ten-to- eleven year-olds who met the criteria.

Research designed to estimate the prevalence of “hyperactivity” provides evidence that from fewer than one percent to as many as twenty percent of school-aged children are considered hyperactive using a variety of different kinds of behavior reporting systems. The wide variety of criteria and lack of rig- orous cross validation undoubtedly contribute to the wide range of estimates.

Prevalence in Clinic Populations Another approach to examining the

prevalence of hyperactivity is to look at the proportion of children seen in child guidance clinics who are “diagnosed” hyperactive.

Kenny et a1 l3 found that, of 100 children referred to a clinic with complaints of hyperactivity, only thirteen were rated hyperactive by all (usually three) clinic observers. Using a similar methodology, Rosen, Bahn and Kramer,23 in surveying the demographic characteristics of psychiatric clinic outpatients in 1961, concluded that the most common diagnosis for school age children was “transient situational personality disorder.” Wender 30 subsequently reported that the most common pediatric diagnosis during latency is hyperactivity.

Symptom Prevalence in the Normal Population

A variety of large-scale epidemiological studies have looked at the preva-

lence of certain behaviors in normal children. These studies provide information on the presence of behavior considered symptomatic of hyperactivity in general childhood populations. A variety of methods were used, including mothers’ reports; l7 teacher check- lists; 32 Q-sorts by mothers; 2Q and ques- tionnaires by mothers and schools.*’ Although these studies have not looked specifically at the diagnosis of “hyperactivity,” they are quite similar to those of H u e s ~ y , ~ Wender,30 and Miller, Palkes and Stewart,lB all of whom used comparable methodology and inferred diag- noses from their data.

Generally, these studies indicated a rather high prevalence of behaviors assumed by others to be “symptoms of hyperactivity.” For example, Lapouse and Monk16 found that the mothers of 482 six-to-twelve-year-olds reported thalt 57% of the boys and 42% of the girls were overactive. Similarly, Werry and Quay32 noted that the teachers of almost 2000 kindergarten ,through second-grade children report that 50% of the boys and 28% of the girls cannot sit still, while 44% of the boys and 26% of the girls have a short attention span. These investigators concluded that the prevalence of such behaviors, which are assumed a priori to be symptomatic of hyperactivity, is so high in normal children that they are of poor diagnostic value. Prevalence studies focused on “hyperactivity,” which use similar in- struments and criteria, should be evaluated in this light.

OBJECTIVES

The investigation reported here set out to identify a large representative sample of children in public and private elementary schools and to estimate the

452 ’ PREVALENCE OF HYPERACTIVITY

Table I DISTRIBUTION OF REPRESENTATIVE POPULATION a BY GRADE LEVEL AND TYPE OF SCHOOL

SCHOOL

GRADE PUBLIC PAROCHIAL PRIVATE TOTAL K I 2 3 4 5 Total

612 709 575 705 694 950 4245

64 I05 I14 46 I27 67 I I2 26 160 I I I26 I 71 I 257

70 I 069 769 043 073

I077 5212

~~~ ~

a Ns denote the representative sample for the home (H) and physician ( P ) defining systems. Since two school dishicts did not supply data requested, the school ( S ) defining system is based on a smaller sample (N’): these figures are available from the suthors, on request.

prevalence of hyperactivity in this population by locating all of the children considered to be hyperactive by parents, physicians, or schools. Several prevalence estimates will be derived, and each will depend on the systems (home, school, and physician) that are primarily responsible for defining hyperactivity in the childhood population.

SAMPLE SELECTION

School Population The sample for this prevalence study

was drawn from the population of Cali- fornia public and private school children in Alameda and Contra Costa counties, the East Bay region of the San Francisco metropolitan area. These two counties contain major urban areas, suburban bedroom communities, and exten- sive rural tracts in the eastern sector. Within the geographic boundaries of these 1500 square miles live 1.7 million individuals from diverse ethnic groups, in various population densities, and following a wide variety of lifestyles.

Sampling Procedure

After listing each of the public and private schools in the two counties, we randomly selected six samples of 40 schools each, one sample for each grade level from kindergarten through fifth. This sampling process produced a list of 240 schools. Five of the 26 public school districts, containing 30 sampled classrooms, decided not to participate; fifteen of the private schools dropped out of the project on religious grounds or because their small, multigraded classrooms were inappropriate for the project; negotiations at the school level failed in four additional cases. The resulting sample consisted of 191 classrooms. TABLE 1 displays the number of children in public, parochial, and private schools by grade level.*

Prevalence Estimates Our estimates of the prevalence of

hyperactivity will be based on the number of identifiable hyperactive subjects in the representative population who

* A breakdown of the number of children in the representative classrooms by grade, sex, and ethnic status is available from the authors.


meet operationally defined and replica- ble definitions of hyperactivity. We employed information from parents, physicians, and school personnel to locate these children, while protecting the rights of the children and their parents.

To obtain information from parents, we contacted by mail all of the parents in the randomly sampled public and private classrooms and asked them to notify us, by returning a form or by a phone call, if their child was considered to be hyperactive and if they would be willing to participate in the project. We sent a Spanish-language form when appropriate.

These methods provided a large sample of hyperactive subjects, but not nec- essarily all of the identified hyperactive children in the representative sample. In order to identify other cases known to the school, we asked teachers, psycholo- gists, principals, nurses, and special educators to compare the names in the representative sample with children known to be considered hyperactive in their school district. The additional cases that they noted were children known to be under treatment for hyperactivity and under the care of the physician, but who had not yet been referred to us by parents or physicians. We asked the school to contact the parents and request per- mission for us to interview them.

Simultaneously with the parent and school identification phase, we asked all of the physicians in the two-county area to refer to us any children they had identified as hyperactive after they obtained parent consent to notify us. To assist the physicians in this process, we listed all of the schools in which the representative sample was located and offered to send them the lists of representative sample pupils in their area. We

were in contact with and received re- ferrals from the major pediatric clinics and hospitals, as well as private physicians. In all cases where parents, physicians, and clinics referred children to us, we followed with a home interview and secured written, informed consent to obtain the child’s school history and medical records.

We recognized that the accuracy of the prevalence estimates would be de- pendent on canvassing parents, physicians, and teachers regarding their per- ceptions of children’s hyperactivity. We asked school personnel to identify by sex and age, but not name, those children they considered to be hyperactive, but whose parents had not responded #to our request to participate. These cases were added to those others identified by the school whose parents were willing to be interviewed, but who did not consider their children to be hyperactive.

The procedures described above provided us with a pool of children considered to be hyperactive by parents, physicians, or educators; it included all of the children to be considered in prevalence estimates. Before determining prevalence estimates, we assigned each child a classification based on the social systems that considered that child hyperactive.

Systems for Defining Hyperactivity Children may be considered hyper-

active or labeled hyperactive by at least three defining systems: the home (H), the school (S), and the physician (P). We have pointed out that many investigators do not consider a child to be hyperactive unless he or she has been judged to be hyperactive by a physician. Other investigators, centering on the school behavior of children, accept the


judgments of the classroom teacher, often formalized by rating procedures, in identifying a child as hyperactive. Recognizing that the behavior of the child may not be the same at home as at school, still other investigators consider that the manifestations of the child’s hyperactive behaviors both at home and at school must be present before hyperactivity is an appropriate label.

The home. A child was considered home-identified if, in response to an interview question, the parents indicated that they considered the child to be hyperactive.

The school. All teachers of the representative classrooms and ather school personnel, such as principals and psy- chologists, were asked to nominate: 1) children who were considered hyperactive, 2) children who, in their opinion, would be considered hyperactive by a physician if their parents would consent to take them for an evaluation, and 3) children who had been referred to a physician for hyperactive behavior for the first time during the current school year. If the replies were in the affirma- tive from these school personnel, we identified the child as one considered to be hyperactive in the school system, and therefore one whose behavior was defined as hyperactive by the social system of the school.

The physician. When we were able to determine that the child had seen a physician for behavior problems associated with hyperactivity, and we had obtained consent for information re- lease, we asked the physician to complete a medical evaluation form. This form was developed in consultation with a group of neurologists, pedia- tricians, and child psychiatrists. The

outcome of this pooling of expertise was an instrument that contained items under the following headings: child’s medical history; physical examination results; laboratory findings; family history; general behavior; school performance; diagnostic summary; and treatment rec- ommendations.

If there were no competing medical explanation of the symptoms (e.g., epi- lepsy) and the physician’s diagnosis was hyperactivity, hyperkinesis, MBD with hyperactivity, or if we could determine that the physician prescribed a cerebral stimulant commonly used with hyperactive children, such as Ritalin or Dexe- drine, we reasoned that the physician considered the child to be hyperactive.

Operational Criteria By applying the definitions of hyper-

activity from these three defining systems, home (H) , school ( S ) , and physician (P), it was possible to define operationally the types of hyperactive subjects on the basis of system definers. These operational definitions are as follows: HSP-children considered hyperactive by all three definers; HP- children considered hyperactive by parents and physicians, but not by educators; SP-children considered hyperactive by physicians and educators, but not by parents.

Many children are considered hyperactive by parents, school, or both, but have not been identified as hyperactive by a physician. Some may not have seen a physician for the presenting problem of hyperactive behavior; parents of others may not have requested such an evaluation; or attending physicians may not have suggested hyperactivity as an explanation of the children’s problems. These children are usually excluded


from studies of hyperactive children, especially drug studies, even though they are included in prevalence estimates of some investigators. They form, nevertheless, important groups of hyperactive children from the perspective of the home and school defining systems.

These subjects make up three additional groups of hyperactive children for prevalence estimates : H C h i l d r e n considered hyperactive by parents and educators; H-children considered hyperactive only by parents; S-children considered hyperactive only by the school.

Behavior Equivalents We have still another method for de-

fining hyperactivity, one that has been used in a number of prevalence studies. In this method, children are defined as hyperactive if their behavior is rated as being in a critical region on a behavior checklist. We used the Behavior and Temperament Survey, which con- sists of a list of 31 behaviors; it is similar to but more comprehensive than Con- ners’s Abbreviated Symptom Question- naire,4 and correlates with the Conners instrument to a high degree ( r= .89) . Other investigators who have used ratings as a source of data to estimate hyperactivity have applied arbitrary cutoff measures based on presumptions of the prevalence of hyperactivity in a childhood population.12 We established the critical region for behavioral equivalents by comparing ratings of identified hyperactive children (i.e., those classified as HSP) with the representative population of peers of their age and sex.

After making a frequency distribution of the total scores on the rating assigned by teachers to the children in the

HSP group, we can locate a cutoff region that will include all the children who have been consensually identified, as well as those with equivalently severe behavior who have not been considered hyperactive. Children not considered hyperactive may be well liked by teachers in spite of their behavior, may be succeeding in school in spite of it, or may have clearly established reasons for their behavior in the teacher’s view.

For our higher bound prevalence estimates we will call any child a behavioral equivalent (BE), regardless of whether the home, school, or physician considered the child hyperactive, whose ratings equaled those earned by the HSP group. Using this method for defining BE children, one obtains another estimate of the prevalence of children evi- dencing hyperactive behaviors based on the number of children whose school behavior can be considered to be similar to that of the HSP hyperactive children, a group of children that has not been labeled otherwise by a critical defining system.

Types of Prevalence Estimates

The above methods of assigning subjects to groups for prevalence estimates determined by defining systems yields nine different estimates of hyperactivity -HSP, HP, SP, HS, H, and S, plus all those identified by H, S, or P regardless of other concurring data. A tenth estimate of hyperactivity, one based solely on teacher ratings of children’s school behavior, provides some indication of the proportion of children in an elementary school whose school behavior can be considered hyperactive but who are not otherwise considered hyperactive by defining systems.


Table 2 PREVALENCE RATES OF CHILDREN IDENTIFIED AS HYPERACTIVE BY IDENTIFYING AGENT

GRADE ~~~

DEFINING SYSTEM K

Home-School-Physician Home-Physician School-Physician Home-School Home only School only

Total by School Total by Home Total by Physician

Total by one or more definers Behavioral Equivalent not

otherwise defined Maximum prevalence

I .28% .26

.38

. I3 2.98 4.64 2.05 I .54 5.03

-

6.65 I 1.68

I 2

1.38% 1.17%

.I2 - - . I 3 - .I3

I .86 3.12 3.36 4.42 I .38 I .43 I .50 1.17 3.36 4.55

- -

8.3 I 8.17 11.67 12.72

3 4

.59% 1.49%

.I2 . I I

.36 -

.47 .23

4.90 3.56 6.32 5.28 1.18 I .83 I .07 I .60 6.44 5.39

- -

8.43 8.3 I 14.87 13.70

5 TOTAL

I.217'0 1.19% .09 .I0 - .08 .09 .2 I - .04

3.44 3.30 4.74 4.78 I .39 I .54 I .30 I .37 4.83 4.92

6.49 7.75 11.32 12.67

DATA COLLECTION AND ANALYSIS

Prevalence Estimates

Essentially the procedure for estimating the prevalence of hyperactivity was to determine the proportion of children in each of the system-defined groups in the representative population of the same grade level. The denominator for thc prevalence estimate was the number of pupils in the grade levels kindergarten through fifth. Two school districts de- clined our request for data from teachers regarding the numbers of children per- ceived to be hyperactive because we had not made this additional task an ex- plicit requirement in our initial contact. The outcome of their decision was that we produced two different denominators for our prevalence estimates. When estimates of the prevalence of hyperactivity are based on the school as a defining system, the denominator for the estimates included only those classrooms on which we had all of the data. The estimates for hyperactivity defined by the school ( S ) as the definer, therefore,

used a smaller number of representative subjects than the estimates of hyperactive children otherwise defined.

RESULTS AND DISCUSSION We will begin the presentation of the

prevalence estimates with an examination of defining systems, with rates broken down by grade level. Next we will set forth prevalence rates as a function of socioeconomic status, sex, and ethnic status. Our strategy will be to pose hypotheses about variations in rates that occur in different sex, age, and social status groups, as well as by various defining systems.

Prevalence Rates as a Function of Definition

Many will be surprised by our finding that the overall prevalence rate of children identified as hyperactive by the home, the school, and the physician (HSP subjects) is only 1.19% of an elementary school population. TABLE 2 displays all the rates derived from our assignment of subjects on the basis of


defining systems. Those in the HSP group can be considered generally comparable to the subjects of clinical trial studies-children who are referred by the school to the parents, who in turn take the children to a physician, who in turn identifies them as hyperactive. I t is the most restrictive definition we have used. This rate is relatively constant across grade levels, being lowest at second and third grades and highest at first and fourth grades.

The constancy of the prevalence rate of the HSP subjects contradicts the assumption that once a child is identified as hyperactive, he continues to be considered hyperactive throughout his school career. If children remained hyperactive and new cases continued to be identified, we would expect an increase in rates as grade level increases.

The prevalence rates for the children defined by combinations of two of the H, S, and P definers are perhaps arti- ficially low, but nevertheless provide some indication that there is not al- ways concurrence with the definition of hyperactivity by parents, physicians, or school when a child enters the identification process. Combinations in which the home is a definer may result in rates that are too low, since not all parents responded to our initial letter in regard to whether or not their child was considered hyperactive. Many parents of hyperactive children do not want to bring additional attention to the children, and many do not wish to participate in research studies. This problem is offset to some extent by our inclusion of the behavioral equivalent group to provide maximum estimates of children evi- dencing hyperactive behaviors. Life history studies can provide information about the variables associated with one

or more of the defining systems not concurring in the identification of a child as hyperactive. One such variable certainly has to be environmental or stressful circumstances that may have an ad- verse impact on the child’s functioning at a particular period.

The assumption of a relationship between environmental factors and identification of hyperactivity constitutes a potential explanation for the peaks in the school prevalence rates reported in TABLE 2. The highest numbers of children considered by the school to be hyperactive occur at kindergarten in the lower primary grades and third grade in the upper primary grades. We dis- covered, in our attempts to locate all of the hyperactive subjects in the representative population, that it often takes about a year after a child is considered hyperative by the school for him to be evaluated and diagnosed by a physician.

A child’s entry into school at kindergarten is considered by many to represent a normal crisis period, followed by increasing demands for independent school learning and conformity with school behavior standards, which result in potentially stressful school demands at third grade. Then, too, at the third grade it also becomes most evident that children who are vulnerable to failure continue to have difficulty learning to read. The peaks in the prevalence rates of the school-identified hyperactive children-higher in kindergarten than in grades one and two; higher in third grade than in grades four and five- doubtlessly reflect children’s reactions to these normal school crisis periods. The peaks in HSP prevalence rates at grades one and four result from a six- month to one-year lag in diagnosis and


treatment from the time of school identification.

I t is of great interest to note that the prevalence rates of the school group do not increase with grade level. If the incidence rates were constant over the elementary years and the children identified at kindergarten, for example, continued to be considered hyperactive as they progressed in school, the prevalence rates would gradually increase with grade level. Such an assumption is not supported by our data. We believe that a more plausible explanation of the variable but relatively similar prevalence rates across grades is that, over time, children move in and out of the group considered to be hyperactive and that this movement reflects changing demands of school and home and different responses of the child’s developing or- ganism interacting with environmental circumstances. The data presented here can neither support nor cast doubt on such propositions, but life history studies of hyperactive children would provide a basis for understanding the course of hyperactivity over time and the factors which affect membership in a hyperactive group at any particular period.

We employed the BE criterion to identify all children in the representative sample who were not otherwise identified as hyperactive. By including these subjects in one of the prevalence rates, we could estimate the number of subjects with behavior similar to the HSP group who had not already en- tered the identification process. TABLE 2 shows the proportion of these children who were not otherwise identified as hyperactive in each representative grade level sample. These data, plus the prevalence rate computed from the numbers

of children who met one or more of the criteria by defining systems, provided a method for estimating the maximum number of children in a grade level who could be considered hyperactive when all of the methods used by other investigators were combined into a single prevalence estimate. TABLE 2 shows that while the overall HSP (those who are most like children in clinical trial studies) prevalence rate is about 1.2%, children considered hyperactive by one or more definers comprise about five percent of the elementary school population. When the BE group not identified by any of the definers is added to this number, the overall prevalence rate rises to between twelve and thirteen percent. These latter values represent the largest number of children in a grade level population who could be consid- wed hyperactive by combining criteria used by other investigators and elimin- ating the overlap occurring when children qualify on multiple criteria.

Prevalence Rates as a Function of Socioeconomic Status

Information about parent’s occupa- tion was available from the parent interview of all of the hyperactive subjects. Occupational status was coded according to the categories in the U.S. Census for 1970. These occupational levels were then grouped into high (pro- fessional, technical, managers, proprie- tors), middle (clerical, sales, crafts- men), and low (operatives, transport workers, laborers, service workers) classifications. Since census data were available on the numbers of employed individuals in these categories, it was possible to determine the proportion of the labor force in these occupational groups in the two-county region from


Table 3 PERCENT O F SUBJECTS IDENTIFIED AS HYPERACTIVE BY DEFIN ING SYSTEMS FROM

DIFFERENT S O C I O E C O N 0 M : C GROUPS

PREVALENCE RATES FOR OCCUPATIONAL LEVEL

DEFIN ING SYSTEMS

Home-School-Physician Home-Physician School-Physician Home-School Home Only School Only

Total by Home Total by School Total by Physician

tracts a t there occupational levels Proportion of adult population in census

HIGH

32.2570 20.00

18.18 IOO.00

17.64 3 I .25 26.60 29.58

30.83

-

MIDDLE

30.65% 40.00 75.00 36.36

41.18 31.25 35.10 33.80

45.67

-

L O W

37.10Y0 40.00 25.00 45.46

41.18 37.50 38.30 36.62

23.49

-

which the representative sample was drawn.

The distribution of occupations of parents of the identified hyperactive subjects is presented in TABLE 3. These data show that socioeconomic status of families of hyperactive children, as inferred from parents’ occupational status, is similar to the distribution in the counties. Some discrepancy will be noted in the proportions of middle-class and lower-class occupational levels. There is a somewhat smaller proportion of middle-class families and a somewhat larger proportion of lower- class families than in the distribution of these occupations in the counties as a whole.

We can conclude from the data dis- played in TABLE 3 that the prevalence of hyperactive children by socioeconomic status is relative proportional to the distribution of socioeconomic status in the general population. Where there

are differences, the rates are somewhat higher than expected for lower socioeconomic groups and lower than expected for the children of middle-class families. These findings suggest, at the least, that medical services are available for children referred for school-related problems of all socioeconomic levels, and that hyperactive children are identified at all socioeconomic levels of the population.

Prevalence Rates as a Function of Sex and Ethnic Status

In general, the prevalence rates for male and female hyperactive children show that boys are from six to eight times more frequently identified as hyperactive than are girls. The prevalence estimates * parallel one another, with the exception that peak rates for girls occur at kindergarten. This may reflect an early appearance of hyperactive behavior in girls which may not be as

-

* A breakdown of the prevalence rates by sex and by ethnic status is available from the authors.


much a function of school attendance as is the occurrence of such behaviors in boys. Such inferences need careful confirmation in longitudinal studies; they are offered here to encourage other investigators to learn more about the characteristics of girls who are defined as hyperactive and to study factors associated with the life period in which hyperactivity in girls and boys is first recognized and treated. Battle and Lacey * also have presented provoca- tive data concerning the interrelations among age, sex, and behavior of overactive children.

The proportion of subjects of the different ethnic groups in the representative sample roughly approximates the proportions reported in the 1970 census of individuals of these ethnic groups residing in the two county area. The prevalence rates * reveal that HSP hyperactive subjects are primarily white. When the rates for the “school only” hyperactive children are examined, blacks and children of Spanish-speaking back- grounds are just as likely to be considered hyperactive as are children who are white. The proportion of black children defined as hyperactive only bv the school is considerably higher than that of the other ethnic groups at third through fifth grades. Certainly one explanation of these differential prevalence rates has to be a function of the interaction of black children’s behavior and the classroom environment. Exactly what behavior constitutes evidence that a particular child is hyperactive in the school needs additional investigation. The reader will also recall in this regard that only half of the children in the school considered to be hyperactive received Behavior and Temperament Scores in the behavior equivalent range.

CONCLUSION The maximum prevalence rate of hy-

peractivity in an elementary school population, when all possible methods for identifying hyperactivity are considered and each child is represented only once in the estimate, is about twelve to thirteen percent. This rate is based on a systematic effort to identify all children in a representative population of over 5000 children who were defined as hyperactive by the home, the school, or the physician, and all those additional children whose behavior was equivalent to the behavior of hyperactive children defined by all three systems. Our estimates provide prevalence rates of children who would receive a diagnosis of hyperactivity after medical referral and evaluation, as well as prevalence rates for the number of children whose behavior is considered “hyperactive” whether or not they have been otherwise defined as hyperactive by the home, the school, or the physician.

Perhaps the best estimate of the prevalence of medically diagnosed hyperactivity in elementary school populations from other researchers comes to us from the work of Kenny and his col- league~.’~ They reported that 41 out of 100 elementary school children referred to a guidance clinic received a medical diagnosis of MBD (minimal brain dysfunction-hyperactive) , but thirteen of them were globally judged to be overactive on the basis of consensus among three observers. We can compare this estimate to our own count of the HSP hyperactive subiects (those who have been referred for medical evaluation).

We found that the HSP rate varied with grade level, beine lowest at third grade ( 5 9 % ) and highest at fourth grade ( 1.49% ). The overall rate across

LAMBERT, SANDOVAL AND SASSONE 46 I

all grade levels was 1.19%. Assuming a hypothetical population of 200 pupils with a rate of referral to child guidance clinics of five percent, the hyperactivity prevalence rate for the Kenny et a1 study would have been .65% in the schools. If the hypothetical referral rate were ten percent, the extrapolated prevalence rate would be 1.30%. These projected figures are very close to the range of prevalence estimates we found in our population. It seems reasonable to conclude that the prevalence rates for diagnosed cases of hyperactivity will vary with age, but range from a low of about .60% to a high of about 1.50%.

When the teachers and other school personnel serving our representative population sample were asked to identify all of the hyperactive subjects in the sampled classrooms, they identified from 3.36% at first grade to 6.32% at third grade as hyperactive (irrespective of other defining systems). Turning to the findings of Miller et U Z , ' ~ we note that when they asked teachers to identify the presence or absence of symptoms of hyperactivity in elementary school children, they produced a prevalence rate of 9.32% of boys and 1.46% of girls, and an overall rate of 5.53%. Similarly, Werner and her co-workers 31 reported a rate of 8.8% of boys, 3.2% of girls, and 5.9% of all children. These estimates are remarkably close to the overall rate of 8.02% of the boys and 1.07% of the girls in our population who were considered to be hyperactive by the school.

Prevalence rates based on teacher rating procedures have been uniformly higher than those based on diagnosed cases or those bnsed on reported school behavior. Both Huessy and Wender built their prevalence estimates on

teacher ratings of behavior, predicting that fifteen to twenty percent of an elementary school population would be hyperactive. Since our baseline data collection process produced teacher ratings on all children in our representative population, we had a good foundation to validate this kind of prevalence estimate. Using an empirically-defined cutoff point on our teacher rating scale, we were able to establish that about ten percent of the representative population could be considered to be hyperactive by one or more defining systems. We explained the obtained proportion of ten percent behavioral equivalent subjects, a figure higher than the six percent that would be predicted from a normal distribution of rating scores, to be a result of differences among teachers in rating practices resulting in restricted ranges of ratings and differences in average ratings of classroom behavior. It is also possible that there is more hyperactive behavior in some classrooms than cthers, which raises important questions about the impact of the classroom environment on the prevalence of hyperactive behavior. We conclude that no more than ten percent of an elementary school population would have behavior equivalent to that of children considered hyperactive bv the home, the school, and the physician.

Although not central to the focus of this report, the extent to which children considered hyperactive received medication to control their behavior is of interest. At the time of our study, 36 of the 62 HSP children (58%) were on medication. While not as large a figure as critics of medication use might pre- dict, it indicates nevertheless how commonly this treatment is used. A future report will consider more fully the


types of treatments recommended and used.

Our maximum prevalence rate of twelve to thirteen percent is somewhat higher than a rate based solely on behavioral equivalent status. Some of the children who were in our prevalence rates and who were not behavior equivalents had low scores, possibly because they were taking medication at the time of the ratings. Other children who the school considered hyperactive did not receive scores high enough on the Be- havior and Temperament Survey to qualify as BE subjects. Only additional study of the psychometric properties of the ratings by classroom and of the behaviors that are crucial to considering children hyperactive at school will provide the needed answers.

The data we have presented do not support the belief that there are cur- rently more hyperactive children than there were in the past. Moreover, our data do not show that the prevalence rates increase with age; if there were an increasing rate we could conclude that there are more children identified each year and that the condition is on the rise. The prevalence rates for hyperactivity, regardless of the method of defining subjects as hyperactive, are relatively similar across the grade levels in an elementary school. We believe that differences in rates are to be explained as a function of the child's constitutional makeup interacting with changing home and school environmental demands.

Children, once they are identified as hyperactive, do not continue to be de- tined as hyperactive throughout the elementary school years. The validity of the assumption of a dynamic interaction of the child with his environmental systems, and the possibility of specify-

ing the factors that influence favorable and unfavorable outcomes, can be evaluated in longitudinal studies. Results could then be compared with the cross- sectional findings that have been presented here, which summarize the prevalence of hyperactivity as a function of social system definers.

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For reprints: Dr. Nadine M. Lambert, School of Education, University of California, Berkeley, Calif. 94720

PREVALENCE OF HYPERACTIVITY IN ELEMENTARY SCHOOL CHILDREN AS A FUNCTION OF SOCIAL SYSTEM DEFINERS

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