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Perceptual and Motor Skills, 2011, 113, 2, 631-646. © Perceptual and Motor Skills 2011

DOI 10.2466/02.06.10.13.PMS.113.5.631-646 ISSN 0031-5125

STRESS AND HAPPINESS AMONG ADOLESCENTS WITH VARYING FREQUENCY OF PHYSICAL ACTIVITY1

INGER ELISE OPHEIM MOLJORD

Department of Nidaros DPS Division of Psychiatry

St.Olavs University Hospital Trondheim, Norway

UNNI KARIN MOKSNES

Research Centre for Health Promotion and Resources HiST/NTNU

Faculty of Nursing Sør-Trøndelag University College

LASSE ERIKSEN

Department of Nidaros DPS Division of Psychiatry

St.Olavs University HospitalDepartment of Neuromedicine

Faculty of Medicine Norwegian University of Science and Technology

GEIR ARILD ESPNES

Research Centre for Health Promotion and Resources HiST/NTNU

Department of Social Work and Health Science Norwegian University of Science and Technology

Summary.—The aim of this cross-sectional study was to investigate associa-tions between physical activity, stress, and happiness, as well as possible sex and age differences on these variables in a survey of 1,508 adolescent pupils (13 to 18 yr.) in middle Norway. Adolescents who reported they participated in physical ac-tivity 2 to 3 times per week or more scored significantly lower on stress and higher on happiness than those who participated in physical activity 1 day per week or less. There was no significant difference on stress and happiness between those be-ing physically active 2 or 3 times a week and those being active almost every day. There was no sex difference in physical activity frequency. Girls had higher mean scores on stress, and boys scored higher on happiness. Adolescents 15 to 16 years old showed higher stress scores than those 17 to18 years old, but there were no significant differences between the different age groups when looking at happiness and physical activity. A statistically significant two-way interaction of sex by age was found on both stress and happiness.

The World Health Organization (WHO) defines health as “complete physical, mental and social well-being and not simply the absence of dis-ease or infirmity” (Nutbeam, 1998, p. 349-364). Better and more exact knowledge of what are positive health predictors are important for devel-oping adequate health promotional strategies among adolescents. Even if one recognizes that most young people in the Western world have rela-tively good health, knowledge about the aforementioned crucial factors is sparse. This could reflect the long-lasting focus in research on health threats and possible disease development rather than on a positive ap-1Address correspondence to Inger Elise Opheim Moljord, Department of Nidaros DPS, Divi-sion of Psychiatry, St.Olavs University Hospital, Østmarkveien 21, Postboks 1893 Lade, 7440 Trondheim, Norway or e-mail (inger.elise.opheim.moljord@stolav.no).

I. E. O. MOLJORD, eT al.632

proach: how to foresee and initiate positive health outcomes. Positive health can be understood as biological, subjective, and functional mea-sures combined in a focus on health rather than illness (Seligman, 2008). Positive health is closely related to a good quality of life, which in turn is related to well-being and happiness (Fordyce, 1988; Veenhoven, 2003). At the same time, personal happiness is viewed as the most important goal to achieve in life (Fordyce, 1988).

Activities or emotions hypothesized as being positive for health de-velopment can also positively influence activities or emotions observed to be negative for health development. Physical activity is such a factor that has been considered positive in this context. In fact, the protective effects of physical activity on several different health aspects have been well doc-umented. It has been shown (Strong, Malina, Blimkie, Daniels, Dishman, Gutin, et al., 2005) that physical activity in adolescence has an important effect on musculoskeletal and cardiovascular health, increases academic performance and self-esteem, and, in addition, reduces symptoms of de-pression and anxiety. It has also been documented (Hallal, Victora, Azeve-do, & Wells, 2006) that physical activity in adolescence provides long-term benefits of bone strength, less risk of breast cancer, and sedentary behav-iours. In particular, swimming and water activities reduce symptoms of asthma and cystic fibrosis. In addition, it has been found that higher fre-quency of physical activity is associated with less depression and anxi-ety and higher self-esteem (Moksnes, Moljord, Espnes, & Byrne, 2010). Others have found that girls report more health complaints than boys, whereas boys report better health (Nesheim & Haugland, 2003). Further, it has been reported that younger children experience better health than older children and that girls experience more stressful events from 12 to 17 years of age (Nesheim & Haugland, 2003; Jose & Ratcliffe, 2004). In an-other study, mean physical activity was shown to decrease significantly from ages 12 to 17 years (Duncan, Duncan, Strycker, & Chaumeton, 2007), which is an interesting finding given this is the same age interval. Sex dif-ferences have been reported on happiness and well-being, where girls re-port being more unhappy and showing lower scores on well-being than boys (Light, 2000; Bergman & Scott, 2001; Jörngården, Wettergen, & von Essen, 2006; Bagøien, Halvari, & Nesheim, 2010). A clear association be-tween age and happiness has been reported related to family situation, where older adolescents are less happy with their family environment (Bergman & Scott, 2001).

Boys have been shown to be more physically active than girls in their leisure time (Trost, Pate, Sallis, Freedson, Taylor, Dowda, et al., 2002; Nesheim & Haugland, 2003; Duncan, et al., 2007; Bagøien, et al., 2010). In the aforementioned study by Moksnes, Moljord, et al. (2010), however, no sex differences were found in frequency of leisure time physical activi-

STRESS AND HAPPINESS AMONG ADOLESCENTS 633

ty. Fleshner (2005) found that physical activity enhances resistance to the negative effects of stress. However, an extensive literature search identi-fied few studies of the effects of physical activity, stress, and happiness on adolescents’ health. In school children, health complaints have been related to school-associated stress and low frequency of physical activ-ity (Haugland, Wold, & Torsheim, 2003). A negative association has been shown between stress and happiness, in which unhappy pupils report-ed more health symptoms than the rest (Natvig, Albrektsen, & Quarn-strøm, 2003). No sex differences have been shown with respect to happi-ness (Natvig, et al., 2003).

Stress is defined here as “environmental events or chronic conditions that objectively threaten the physical and/or psychological health or well-being of individuals of a particular age in a particular society” (Grant, Compas, Stuhlmacher, Thurm, McMahon, & Halpert, 2003, p. 462). Arous-al and stress are experienced at different intensities and durations during adolescence and have different effects on each individual (Grant, et al., 2003). The occurrence of stressful events seems to increase with age dur-ing this period. Researchers have reported that girls appear to be more vulnerable to stress than boys (Rudolph & Hammen, 1999; Brooks, Harris, Thrall, & Woods, 2002; Jose & Ratcliffe, 2004; Hampel & Petermann, 2006; Rose & Rudolph, 2006). Boys seem to experience most stress in relation to external events (Rudolph & Hammen, 1999; Rudolph, 2002), whereas girls seem to be more emotionally sensitive and report more interperson-al stress and strain associated with relationships with parents and friends (Rudolph & Hammen, 1999; Rudolph, 2002; Hampel & Petermann, 2006; Rose & Rudolph, 2006). Humor seems to be a more frequent behavioural response to stress in boys than in girls (Rose & Rudolph, 2006), under-stood to be a coping strategy.

Happiness can be understood as an outcome of life, and therefore dis-tinct from preconditions for a good life, such as a livable environment (good living conditions) and good life skills. Good life skills can be defined as “how well we are equipped to cope with the problems of life” (Veen-hoven, 2003). Happiness may also refer to an intense positive emotion and as a general evaluation of life as a whole. Self-reported happiness is strongly correlated with well-being, contentment, pleasure, and satisfac-tion, and an absence of negative affect (Diener, Oishi, & Lucas, 2003; Vit-tersø, Oelman, & Wang, 2007). Frequent positive affect is both fundamen-tal and sufficient for the experience of happiness and for high scores on happiness measures (Diener, Sandvik, & Pavot, 2009). In previous stud-ies, factors such as teachers’ support, satisfaction with school and school experiences, living environment, self-efficacy, and general life satisfaction have been central factors in the perception of life satisfaction and happi-

I. E. O. MOLJORD, eT al.634

ness among adolescents (Natvig, et al., 2003; Gilman, Huebner, Tian, Park, O’Byrne, Schiff, et al., 2008). Furthermore, Natvig, et al. (2003) have shown that happy adolescents experience more support and fewer health prob-lems (including psychosomatic symptoms).

Physical and psychological benefits have been associated with physi-cal activity (Lotan, Merrick, & Carmeli, 2005). Physical activity among ad-olescents plays a positive role in association with stress and leads to bet-ter resistance to negative effects of stress (Haugland, et al., 2003; Fleshner, 2005; Penedo & Dahn, 2005). Even walking daily for 30 minutes at a mod-erate intensity, which is considered as small increases in physical activity, has been shown to give substantial beneficial health effects (Anderssen & Strømme, 2001; Haskell, Lee, Pate, Powell, Blair, Franklin, et al., 2007).

The present study examined the relations of physical activity, stress, and happiness in a sample of Norwegian adolescents 13 to 18 years old in junior and senior high schools in rural communities. The hypotheses of the present study, based on the literature review, were: (1) adolescents with a low self-reported frequency of physical activity would score sig-nificantly higher on stress and lower on happiness than adolescents with moderate and high self-reported frequency of physical activity; (2a) boys would score significantly higher on mean physical activity than girls, (2b) girls would score significantly higher on mean stress than boys, (2c) boys would score significantly higher on mean happiness than girls, (2d) there would be a significant difference across age groups in physical activity, stress, and happiness; and (3) there would be a significant interaction ef-fect of sex by age by stress on physical activity and happiness.

MethodParticipants

The study was based on cross-sectional data from a large study called “Growing up in rural settings in Mid-Norway.” Adolescents from elemen-tary and secondary schools in six rural communities of one county par-ticipated. A total of 2,341 adolescents was asked to participate (1,648 from senior high school and 693 from junior high school). A total of 1,862 par-ticipants completed the questionnaires, a response rate of 79.5%. Missing responses were mainly due to noncooperation of classes or students being absent when the questionnaire was administered. In the present study, the age range was restricted to adolescents 13 to 18 years old, and the analyses were therefore undertaken for N = 1,508 students (81% of the total of 1,862 participants). Of the participants, 769 (51.1%) were girls and 735 (48.9%) were boys (four participants did not report sex). The mean age for girls was 15.0 yr. (SD = 1.6) and for boys 14.8 yr. (SD = 1.5). The mean age of the whole group was 14.9 yr. (SD = 1.5).

STRESS AND HAPPINESS AMONG ADOLESCENTS 635

ProcedureThe study was reported and carried out according to the rules of the

Norwegian Social Science Data Service. Consent was given by the mu-nicipalities and the schools. The youth and their parents received a letter, which explained the intention of the study. During data collection, it was emphasized that participation was voluntary, anonymous, and confiden-tial, and no identity data were collected. Questionnaires were distributed to the schools directly and were administered to the classes during one class hour under supervision from teachers, which gave a high response rate. As far as possible, the questionnaires were given at the same time to all classes. Measures

Demographic measures included age, sex, and school grade. Physical activity was measured using one item: “During the last four weeks, how many days per week have you participated in sports or physical activity so hard that you had high respiratory frequency, sweated, or had an in-creased heart rate for at least 20 min. (or more)?” The response categories were: 1: Never, 2: Less than one day a week, 3: One day a week, 4: Two or three days a week, and 5: Mostly every day during the week. The ques-tion was adapted from Kurtze, Gundersen, and Holmen (2003). The ques-tion has been validated, and reliability tested. Test-retest reliability of fre-quencies (8–12 days) was .73 in Rangul, Holmen, Kurtze, Cuypers, and Midthjell (2008).

Stress.—Stress was assessed using the Norwegian version of the Ado-lescent Stress Questionnaire (Moksnes, Byrne, Mazanov, & Espnes, 2010), which is a 58-item questionnaire (Byrne, Davenport, & Mazanov, 2007) on common adolescent stressors rated on a 5-point scale: 1: Not stressful or irrelevant to me, 2: A little stressful, 3: Moderately stressful, 4: Quite stressful, and 5: Very stressful. This questionnaire has been continuous-ly developed and validated by Byrne, et al. (2007). The Norwegian ver-sion has been validated for use in Norwegian adolescent samples (Mok-snes, Byrne, et al., 2010). The factor analysis on the Total stress scale shows nine dimensions associated with (1) teacher/adult interaction, (2) peer pressure, (3) home life, (4) adult responsibility, (5) romantic relationships, (6) school attendance, (7) school/leisure conflict, (8) school performance, and (9) financial pressure. As in the study of Mazanov and Byrne (2008), the responses in the current study were summed to give a Total score. These summed scores had a minimum score of 58 and a maximum score of 287 for the 58 items. The stress scale was divided into three statistically equal-sized groups: Low stress = 58–100, Moderate stress = 101–149, and High stress = 150–287 (Moksnes, Byrne, et al., 2010). Cronbach’s alpha in

I. E. O. MOLJORD, eT al.636

the present study was .97, which reflects a very good reliability (Carmines & Zeller, 1994; Nunnally & Bernstein, 1994). No other estimates of reliabil-ity or validity were conducted.

Happiness.—Happiness was measured using the Fordyce Happiness Scale, based on the work of Wessman and Ricks (1966) and improved and validated by Fordyce (1988). This scale has three items assessing the per-centage of time a respondent feels happy, neutral, or unhappy based on a Likert-type rating. The present study used a 1-item scale with an 11-point answer category from 0–10, which is a measure of intensity (or quality) of happiness (Fordyce, 1988). The question was, “How happy or pleased have you been during the last week?” with response categories based on: 0: Extremely unhappy, 1: Very unhappy, 2: Quite unhappy, 3: Moderately unhappy, 4: A little unhappy, 5: Neutral, 6: A little happy, 7: Moderately happy, 8: Quite happy, 9: Very happy, and 10: Extremely happy.

The test-retest reliabilities for the Fordyce Happiness Scale were .98 for a 2-day period and .86 to .88 for a 2-wk. period, .81 for 1 mo. for the combination scores, and acceptable test-retest correlation coefficients ranging from .59 to .85 over time intervals of 1.5–15 wk. (Fordyce, 1988; Toussaint & Friedman, 2009). Reliability of this measure has been shown to be comparable to values for the intensity scores (Fordyce, 1988). The Happiness Scale has shown good discriminant and construct validities in several studies, and a strong and consistent convergence with a wide array of recognized happiness, well-being, and emotional instruments (Fordyce, 1988; Hormes, Lytle, Gross, Ahmed, Troxel, & Schmitz, 2008; Toussaint & Friedman, 2009). analysis

Data were screened for missing values and outliers. The missing rate was relatively low for the different variables: 0.3% (sex), 1.1% (physical activity), 9.4% (stress), and 16% (happiness). The sample of missing data was random (MCAR; Allison, 2001). For respondents with up to 25% miss-ing responses within a scale, missing responses were replaced with modes (Mazanov & Byrne, 2008). For respondents with more than 25% missing responses within a scale, no score was calculated. Missing items were treated the same in all the analyses.

Means and standard deviations, including frequencies and ratings, were calculated for the variables of physical activity, stress, and happi-ness. Pearson correlations were calculated to estimate the bivariate as-sociations between the variables used. Multivariate analyses of variance (MANOVAs) were used to assess sex and age differences on the outcome of physical activity, stress, and happiness (two-way between-groups), as well as how sex, age, and stress are associated with the outcome of physi-cal activity and happiness (three-way between-groups). Preliminary as-

STRESS AND HAPPINESS AMONG ADOLESCENTS 637

sumption testing was conducted to check for normality, linearity, univari-ate and multivariate outliers, homogeneity, variance-covariance matrices, and multicollinearity, with no serious violation noted. Wilks’ Lambda was used to evaluate the significance of all multivariate effects, and the alpha level was set to .05. In the three-way between-groups comparison, the stress scale with a range of 58–287 was divided into three groups: Low stress = 58–134, Moderate stress = 135–210, and High stress = 211–287.

Bonferroni’s post hoc procedure was applied to assess mean values be-tween groups on the dependent variables of physical activity, stress, and happiness, because Bonferroni-adjusted alpha reduces the risk for Type 1 errors. To analyze possible age differences, ages (13 to 18 years) were di-vided into three groups: Group 1, 13 to 14 years; Group 2, 15 to 16 years; and Group 3, 17 to 18 years.

A one-way between-groups analysis of variance applying Bonferro-ni’s post hoc adjustment to tests was performed to examine whether mean group differences were significant for physical activity on the dependent variables of stress and happiness. Physical activity was divided into three groups with Low = 1 day or less per week, Moderate = 2–3 days per week, and High = most days per week. These categories were based on frequen-cy distributions and an understanding of these categories as reflecting re-ports of low, moderate, and high physical activity.

Partial eta squared (η²; effect size) ranges from 0 to 1 and represents the proportion of variance in the dependent variable explained by the in-dependent (group) variable as small (η² = .01), medium (η² = .09), and large (η² = .25) effects (Tabachnick & Fidell, 2007). The statistical analyses were carried out using SPSS Version 14 (SPSS, Inc., 2003).

ResultsIn the present study, 69.8% of the adolescents reported they were

physically active 2–3 days per week (26.3% of those were physically active almost every day), while 30.2% reported that they were physically active 1 day or less per week (4% of those were not physically active at all). The mean score for the whole sample on stress was 129.8, and the mean score on happiness was 7.7. Distribution of sex and age differences on the out-come of physical activity, stress, and happiness is shown in Table 1.

The results from correlations between age, physical activity, stress, and happiness are presented separately for boys and girls in Table 2. As shown, a weak positive, but statistically significant, correlation was found between physical activity and happiness, and a statistically significant negative correlation between stress and happiness for girls, whereas for boys, a statistically significant positive correlation was found between happiness and physical activity, and a negative statistically significant cor-relation was found between stress and physical activity.

I. E. O. MOLJORD, eT al.638

TABL

E 1

Mea

ns, S

tand

ard

Dev

iati

ons,

and

Perc

enta

ge o

f Sex

and

Age

Dis

trib

utio

n of

Par

tici

pant

s in

Gro

up 1

: 13–

14-y

r.-o

ld,

Gro

up 2

: 15–

16-y

r.-o

ld, a

nd G

roup

3: 1

7–18

- yr.

-old

(N = 

1,50

8) o

n Ph

ysic

al A

ctiv

ity,

Stre

ss, a

nd H

appi

ness

Age

, Phy

sica

l Act

ivity

, Str

ess,

an

d H

appi

ness

Gir

lsBo

ysTo

tal

n%

MSD

n%

MSD

n%

MSD

Gro

up 1

: 13–

14 y

r.34

3 4

4.6

349

47.

569

2 4

6.0

Phy

sica

l act

ivity

339

3.8

1.0

342

3.9

1.1

3.9

1.0

Str

ess

313

137.

551

.030

612

0.6

45.4

129.

049

.1 H

appi

ness

288

7.8

2.2

281

7.9

1.9

7.8

2.1

Gro

up 2

: 15–

16 y

r.27

3 3

5.5

276

37.

654

9 3

6.5

Phy

sica

l act

ivity

273

3.7

1.0

273

3.9

1.0

3.8

1.0

Str

ess

257

147.

348

.624

311

9.4

40.3

133.

746

.8 H

appi

ness

244

7.2

2.5

224

8.0

2.0

7.6

2.3

Gro

up 3

: 17–

18 y

r.15

3 1

9.9

110

15.

026

3 1

7.5

Phy

sica

l act

ivity

152

3.7

1.0

108

3.7

1.0

3.7

1.0

Str

ess

142

130.

441

.910

111

3.9

41.5

123.

543

.0 H

appi

ness

132

7.5

2.1

947.

71.

87.

52.

01To

tal g

roup

769

100.

073

510

0.0

1,50

410

0.0

Phy

sica

l act

ivity

764

3.8

1.0

723

3.9

1.0

1,48

73.

81.

0 S

tres

s71

213

9.6

49.0

650

119.

142

.91,

362

129.

847

.3 H

appi

ness

664

7.5

2.3

599

7.9

1.9

1,26

37.

72.

1

STRESS AND HAPPINESS AMONG ADOLESCENTS 639

A one-way between-groups analysis of variance (ANOVA) was con-ducted to investigate the association among different frequencies of phys-ical activity when divided into three groups (Low, Moderate, High) and the outcome of stress and happiness scores. There was a statistically sig-nificant difference in mean stress scores for the three groups (Table 3). The post hoc test showed that the group with Low frequency of physical activ-ity had a statistically significantly higher mean score on stress than the Moderate activity (p = .014) and High activity (p = .003) groups. There was, however, no statistically significant difference in mean stress score for groups with Moderate and High frequencies of physical activity (p = 1.00).

There was a significant difference in happiness for the three groups reporting different physical activity levels. Post hoc comparisons showed that the group with Low frequency of physical activity had a statistically significantly lower mean score on happiness than the Moderate (p = .001) and High (p < .001) activity groups. There was, however, no statistically significant difference (p = .060) in mean happiness scores for the Moderate and High activity groups.

TABLE 2Pearson Correlations (95%CI) of Age, Physical Activity, and Scores on Stress, and Happiness For Girls and Boys

Age 95%CI Physical Activity

95%CI Stress 95%CI

GirlsAgePhysical activity −.02 −.10, .05Stress −.04 −.11, .04 −.13* −.21, −.05Happiness −.06 −.13, .01 .15* .07, .24 −.33* −.40, −.26

BoysAge _Physical activity −.01 −.10, .07Stress −.05 −.13, .04 −.08 −.17, .01Happiness −.02 −.11, .06 .18* .09, .28 −.31* −.41, −.22

Note.—640 girls, 566 boys, listwise analysis. *p ≤ .01 (two-tailed).

TABLE 3Main Effects of Physical Activity on Dependent Variables of Stress and Happiness

M SD df F p η²

Stress 2 6.23 .002 .01Low frequency of physical activity 136.01 48.21Moderate freq. of physical activity 126.93 47.21High freq. of physical activity 124.26 44.61

Happiness 2 14.50  < .001 .02Low freq. of physical activity 7.21 2.42Moderate freq. of physical activity 7.72 2.02High freq. of physical activity 8.07 1.90

*p ≤ .05.

I. E. O. MOLJORD, eT al.640

The two-way between-groups MANOVA showed that the multivari-ate test of sex and age on physical activity, stress, and happiness was sta-tistically significant. There were main effects of sex (F3,1198 = 14.95, p < .001; Wilks’ Lambda = 0.96; η² = 0.04) and age (F6,2396 = 2.35, p = .029; Wilks’ Lamb-da = 0.99; η² = 0.006). The multivariate interaction of sex by age was mar-ginally significant (F6,2396 = 2.14, p = .05; Wilks’ Lambda = 0.99; η² = 0.005).

When the results were considered separately, they showed no statis-tically significant main effect of sex on physical activity (Table 4). There was a statistically significant main effect of stress and happiness. Girls had higher mean scores on stress and lower mean scores on happiness than boys. When looking at age, a statistically significant main effect was found on stress but not on physical activity or happiness. Adolescents 15 to 16 years of age had statistically significantly higher mean stress scores than adolescents 17 to 18 years of age. There was no statistically significant dif-ference between the age groups on happiness and physical activity. The interactions of sex by age on stress and happiness were statistically sig-nificant. Girls had higher mean scores on stress and lower mean scores on happiness than boys in all age groups.

A three-way between-groups MANOVA to investigate the three-way interaction of sex, age, and stress on physical activity and happiness was conducted. The interaction was not statistically significant.

DiscussionThe results show that a change in the frequency of physical activity

from 1 day or less a week to 2–3 days, or 1 day or less per week to almost every day per week, was associated with a statistically significant change in stress and happiness. That is, a change from being almost physically in-active or reporting a low frequency of physical activity to being moderate-ly or highly physically active was associated with reports of lower stress and higher happiness. This is in line with Hypothesis 1. For higher fre-quency activity, a comparison of doing physical activity 2–3 days a week and almost every day indicate a weak but not significant difference on stress and happiness. This may not be surprising, as the biggest change re-

TABLE 4Main Effects and Interaction Effects of Sex and Age on Physical Activity, Stress, and Happiness

Physical Activity Stress Happiness

df F p η² df F p η² df F p η²Sex 1 2.35 .13 0.002 1 43.98  < .001 .035 1 7.34 .007 .006Age 2 0.25 .78 < 0.001 2 4.45 .01 .007 2 1.75 .17 .003Sex × Age 2 2.27 .10 0.004 2 3.11 .05 .005 2 3.29 .04 .005Note.—η² indicates effect sizes.

STRESS AND HAPPINESS AMONG ADOLESCENTS 641

garding the health gains of physical activity has been shown when people move from being least physically active to moderately or highly physical-ly active (Anderssen & Strømme, 2001). However, it has also been found that the more physically active the youth were, the better health they re-ported (Nesheim & Haugland, 2003). The negative association of physical activity with stress has been previously reported (Haugland, et al., 2003; Fleshner, 2005; Penedo & Dahn, 2005), and this is also the case with the positive association of happiness with physical activity (Dishman, Motl, Saunders, Felton, Ward, Dowda, et al., 2005; Penedo & Dahn, 2005). In the study by Moksnes, Moljord, et al. (2010), however, physical activity did not moderate the relation between overall stress and psychological func-tioning (depression, anxiety, and self-esteem).

The data do not support Hypothesis 2a, that boys would report sig-nificantly higher mean physical activity than girls. This is not consistent with a number of previous findings (Trost, et al., 2002; Nesheim & Haug-land, 2003; Duncan, et al., 2007; Sherar, Esliger, Baxter-Jones, & Tremblay, 2007; Moksnes, Moljord, et al., 2010). However, it has been reported that sex differences in actually partaking in physical activity have been small-er than those from self-report methods to assess physical activity (Trost, et al., 2002). This may reflect that the item used in this study assessed the actual occurrence of physical activity.

Girls reported statistically significantly higher stress than boys, but the effect size was low. This result supports Hypothesis 2b, and indicated sex differences with respect to stress, which is in line with results of pre-vious studies (Rudolph & Hammen, 1999; Brooks, et al., 2002; Jose & Rat-cliffe, 2004; Fleshner, 2005; Hampel & Petermann, 2006; Rose & Rudolph, 2006). Increased stress during adolescence seems to be more common in girls than boys. This result is in accord with the findings of Jörngården, et al. (2006) and Nesheim and Haugland (2003), showing that boys gener-ally report better health and experience life more positively than girls of the same age, which may be a reflection of the findings (Rose & Rudolph, 2006) that boys are more likely to use humor as a response to stress.

In the study by Moksnes, Byrne, et al. (2010), girls were found to be more responsive to different situations that may be recognized as stress-ful; girls scored higher on all dimensions of stress. A slightly different and possibly further explanation of this responsiveness could be that adoles-cent girls have increased risk for stress due to more highly developed in-terpersonal relationships than boys. Girls seem to experience more inter-personal stress, more negative interpersonal events, and greater increase in emotional problems than boys (Rudolph & Hammen, 1999; Rudolph, 2002; Hampel & Petermann, 2006; Rose & Rudolph, 2006). Girls seem to be more preoccupied with negative thoughts about their friends and ex-perience negative affects with peers and family groups. They also tend to

I. E. O. MOLJORD, eT al.642

experience more stress in the transition from preadolescence to adoles-cence than boys (Rudolph, 2002). There is one report of a statistically sig-nificant negative association between school stress and happiness (Nat-vig, et al., 2003), but the authors did not find sex differences for happiness. In the present study, boys showed a significantly higher mean on happi-ness than girls, which is in accordance with Hypothesis 2c. The effect size was moderate.

The present study further investigated how physical activity, stress, and happiness might change during adolescence across the different age groups. When looking at the interaction of physical activity and age group, the mean scores on physical activity did not differ statistically significantly between the three age groups. These results therefore did not support Hy-pothesis 2d, and are not in line with previous findings in other studies of adolescents showing a clearer decrease in physical activity across the age span (Trost, et al., 2002; Duncan, et al., 2007; Sherar, et al., 2007).

In the present study, the interaction of stress and age indicated a sig-nificant difference between the 15- to 16-yr.-olds and the 17- to 18-yr.-olds. When considering boys and girls separately, the girls’ mean stress scores increased across 13- to 14-yr. and 15- to 16-yr. age groups and then de-creased for the 17- to 18-yr. age group. The boys’ mean stress scores de-creased across age groups and was consistently lower than the girls’ mean stress scores. The effect sizes showed, however, that the differences in mean scores were small for the different age groups. Other studies (Ru-dolph, 2002; Jose & Ratcliffe, 2004) have found that stress increased during the adolescent period, which corresponds with the mean for girls between 13 and 16 years of age in the present study. Stress seems to fluctuate with age in a quite specific pattern and is in line with Hypothesis 2d. The inter-action of happiness and age showed no statistically significant difference. Happiness ratings may not have fluctuated with age; this is not in line with Hypothesis 2d. When investigating Hypothesis 3, the interaction ef-fect of Sex by Age by Stress on physical activity and happiness, there was no support for the hypothesis.

The strengths of the present study are the large sample size, the high response rate, and the relatively low rate of missing data with a random pattern. The study has some limitations concerning the possibility of drawing general conclusions. Firstly, the sample is drawn from one sin-gle county in Norway. In order to minimize the problems rising from a homogeneous sample, the study would have had to employ schools from six very different municipalities across the county, from coastal munici-palities to municipalities in the mountains. The study is based on self-report data with only one time assessment of subjective experiences of happiness, stress, and participation in physical activity. This methodology involves possible over- or underestimates, which can contribute to bias

STRESS AND HAPPINESS AMONG ADOLESCENTS 643

and misclassifications. However, the method is often used and seems to give a fairly good indication of the associations between physical activity, stress, and happiness (Brooks, et al., 2002; Haugland, et al., 2003; Nesheim & Haugland, 2003; Gerber & Pühse, 2008; Moksnes, Moljord, et al., 2010).

Physical activity was measured on a single item, which measured the frequency (days per week) and duration (hours and minutes). The use of scales or complex measures might have led to an increased estimate of re-liability. Haugland, et al. (2003), Gerber and Pühse (2008), and Moksnes, et al. (2010) have, however, measured physical activity by using one sin-gle item. The ideal measure of physical activity would include items of frequency, intensity, and duration (Shephard, 2003). Physical activity was measured based on physical activity during the last 4 wk., stress during the last year, and happiness during the last week. These differences may have been reflected in the results. In future studies, objective measure-ment of physical activity would be an alternative to traditional self-report methods or a combination of both methods. This would imply a consider-able use of time and other resources, which are usually not available.

In conclusion, adolescents with high-to-moderate self-reported phys-ical activity reported significantly lower stress and higher happiness than adolescents with low self-reported physical activity. There seems to be no important sex difference in frequency of physical activity in this sample. Girls reported more stress than boys, and boys greater happi-ness than girls. No significant differences were found among the differ-ent age groups with respect to physical activity. Reported stress, however, decreased for girls from 15–16 to 17–18 years of age, while for boys stress decreased from 13 to 14 years. No statistically significant differences were found among the different age groups on scores of happiness. High or moderate frequency of physical activity seems to be important for ado-lescents’ health and well-being. Therefore, focus on physical activity in school and in leisure time activity is important to promote motivation and interest in participation.

REFERENCES

Allison, P. D. (2001) Missing data. Thousands Oaks, CA: Sage.Anderssen, S. A., & Strømme, S. B. (2001) Fysisk aktivitet og helse anbefalinger

[Physical activity and health recommendations]. Tidsskrift for Den Norske Lege-forening [ Journal of the Norwegian Medicine association], 121, 2037-2041.

Bagøien, T. E., Halvari, H., & Nesheim, H. (2010) Self-determined motivation in physi-cal education and its links to motivation for leisure-time physical activity, physical activity, and well-being in general. Perceptual and Motor Skills, 111, 407-432.

Bergman, M. M., & Scott, J. (2001) Young adolescents’ well-being and health-risk be-haviours: gender and socio-economic differences. Journal of adolescence, 24, 183-197.

I. E. O. MOLJORD, eT al.644

Brooks, T. L., Harris, S. K., Thrall, J. S., & Woods, E. R. (2002) Associations of ado-lescent risk behaviours with mental health symptoms in high school students. Journal of adolescent Health, 31, 240-246.

Byrne, D. G., Davenport, S. C., & Mazanov, J. (2007) Profiles of adolescent stress: the development of the Adolescent Stress Questionnaire (ASQ). Journal of adolescence, 30, 393-416.

Carmines, E. G., & Zeller, R. A. (1994) Reliability and validity assessment. In M. S. Lewis-Beck (Ed.), Basic measurement: international handbooks of quantitative applica-tions in the social sciences. London: Sage. Pp. 1-58.

Diener, E., Oishi, S., & Lucas, R. E. (2003) Personality, culture, and subjective well-being: emotional and cognitive evaluations of life. annual Review of Psychology, 54, 403-425.

Diener, E., Sandvik, E., & Pavot, W. (2009) Happiness is the frequency, not the in-tensity, of positive versus negative affect. In E. Diener (Ed.), assessing well-being: the collected works of ed Diener. Social Indicators Research Series, Vol. 39. London: Springer. Pp. 213-231.

Dishman, R. K., Motl, R. W., Saunders, R., Felton, G., Ward, D. S., Dowda, M., & Pate, R. R. (2005) Enjoyment mediates effects of a school-based physical-activity inter-vention. Medicine & Science in Sports & exercise, 37, 478-487.

Duncan, S. C., Duncan, T. E., Strycker, L. A., & Chaumeton, N. R. (2007) A cohort- sequential latent growth model of physical activity from ages 12 to 17 years. an-nals of Behavioral Medicine, 33, 80-89.

Fleshner, M. (2005) Physical activity and stress resistance: sympathetic nervous sys-tem adaptations prevent stress-induced immunosuppression. exercise and Sport Sciences Reviews, 33, 120-126.

Fordyce, M. (1988) A review of research on the happiness measure: a sixty second index of happiness and mental health. Social Indicators Research, 20, 355-381.

Gerber, M., & Pühse, U. (2008) “Don’t crack under pressure!” Do leisure time physi-cal activity and self-esteem moderate the relationship between school-based stress and psychosomatic complaints? Journal of Psychosomatic Research, 65, 363-369.

Gilman, R., Huebner, E. S., Tian, L., Park, N., O’Byrne, J., Schiff, M., Sverko, D., & Langknecht, H. (2008) Cross-national adolescent multidimensional life satisfac-tion reports: analyses of mean scores and response style differences. Journal of Youth and adolescence, 37, 142-154.

Grant, K. E., Compas, B. E., Stuhlmacher, A. F., Thurm, A. E., McMahon, S. D., & Halpert, J. A. (2003) Stressors and child and adolescent psychopathology: mov-ing from markers to mechanisms of risk. Psychological Bulletin, 129, 447-466.

Hallal, P. C., Victora, C. G., Azevedo, M. R., & Wells, J. C. K. (2006) Adolescent physical activity and health: a systematic review. Sports Medicine, 36, 1019-1030.

Hampel, P., & Petermann, F. (2006) Perceived stress, coping, and adjustment in ado-lescents. Journal of adolescent Health, 38, 409-415.

Haskell, W. L., Lee, I-M., Pate, R. R., Powell, K. E., Blair, S. N., Franklin, B. A., Macera, C. A., Heath, G. W., Thompson, P. D., & Bauman, A. (2007) Physical activity and public health: updated recommendation for adults from the Ameri-can College of Sports Medicine and the American Heart Association. Medicine & Science in Sports & exercise, 39, 1423-1434.

Haugland, S., Wold, B., & Torsheim, T. (2003) Relieving the pressure? The role of physical activity in the relationship between school-related stress and adolescent health complaints. Research Quarterly for exercise and Sport, 74, 127-135.

STRESS AND HAPPINESS AMONG ADOLESCENTS 645

Hormes, J. M., Lytle, L. A., Gross, C. R., Ahmed, R. L., Troxel, A. B., & Schmitz, K. H. (2008) The Body Image and Relationships Scale: development and validation of a measure of body image in female breast cancer survivors. Journal of Clinical Oncology, 26, 1269-1274. R I

Jörngården, A., Wettergen, L., & von Essen, L. (2006) Measuring health-related quality of life in adolescents and young adults: Swedish normative data for the SF–36 and the HADS, and the influence of age, gender, and method of administra-tion. Health and Quality of life Outcomes, 4, 1-10. DOI:10.1186/1477-7525-4-91.

Jose, P. E., & Ratcliffe, V. (2004) Stressor frequency and perceived intensity as predic-tors of internalizing symptoms: gender and age differences in adolescence. New Zealand Journal of Psychology, 33, 145-154.

Kurtze, N., Gundersen, K. T., & Holmen, J. (2003) Self-reported physical activity in population studies: a methodological problem. Norwegian Journal of epidemiology, 13, 163-170.

Light, H. (2000) Sex differences in indicators of well-being in adolescents. Psychologi-cal Reports, 87, 531-533.

Lotan, M., Merrick, J., & Carmeli, E. (2005) Physical activity in adolescence: a review with clinical suggestions. International Journal of adolescent Medicine and Health, 17, 13-21.

Mazanov, J., & Byrne, D. G. (2008) Modelling change in adolescent smoking behav-iour: stability of predictors across analytic models. British Journal of Health Psychol-ogy, 13, 361-379.

Moksnes, U. K., Byrne, D. G., Mazanov, J., & Espnes, G. A. (2010) Adolescent stress: evaluation of the factor structure of the Adolescent Stress Questionnaire (ASQ–N). Scandinavian Journal of Psychology, 51, 203-209.

Moksnes, U. K., Moljord, I. E., Espnes, G. A., & Byrne, D. G. (2010) Leisure time physical activity does not moderate the association between stress and psycho-logical functioning in Norwegian adolescents. Journal of Mental Health and Physical activity, 3, 17-22.

Natvig, G. K., Albrektsen, G., & Quarnstrøm, U. (2003) Associations between psy-chosocial factors and happiness among school adolescents. International Journal of Nursing Practice, 9, 166-175.

Nesheim, T., & Haugland, S. (2003) Fysisk aktivitet og opplevd helse blant norske 11–15 åringer [Physical activity and perceived health among adolescents 11 to 15 years old]. Tidsskrift for Den Norske Legeforening [Journal of the Norwegian Medical association], 123, 772-774.

Nunnally, J. C., & Bernstein, I. H. (1994) Psychometric theory. (3rd ed.) New York: McGraw-Hill.

Nutbeam, D. (1998) Health promotion glossary. Health Promotion International, 13, 349-364.

Penedo, F. J., & Dahn, J. R. (2005) Exercise and well-being: a review of mental and physical health benefits associated with physical activity. Current Opinion in Psy-chiatry, 18, 189-193.

Rangul, V., Holmen, T. L., Kurtze, N., Cuypers, K., & Midthjell K. (2008) Reliability and validity of two frequently used self-administered physical activity question-naires in adolescents. BMC Medical Research Methodology, 8, 47. DOI:10.1186/1471-2288-8-47.

I. E. O. MOLJORD, eT al.646

Rose, A. J., & Rudolph, K. D. (2006) A review of sex differences in peer relationship processes: potential trade-offs for the emotional and behavioural development of girls and boys. Psychological Bulletin, 132, 98-131.

Rudolph, K., & Hammen, C. (1999) Age and gender as determinants of stress expo-sure, generation, and reaction in youngsters: a transactional perspective. Child Development, 70, 660-677.

Rudolph, K. D. (2002) Gender differences in emotional responses to interpersonal stress during adolescence. Journal of adolescent Health, 30, 3-13.

Seligman, M. E. P. (2008) Positive health. International association of applied Psychol-ogy: an International Review, 57, 3-18.

Shephard, R. J. (2003) Limits to the measurement of habitual physical activity by questionnaires. British Journal of Sports Medicine, 37, 197-206.

Sherar, L. B., Esliger, D. W., Baxter-Jones, A. D. G., & Tremblay, M. S. (2007) Age and gender differences in youth physical activity: does physical maturity matter? Medicine & Science in Sports & exercise, 39, 830-835.

SPSS, Inc. (2003) SPSS advanced statistics 14.0. Chicago, IL: Author.Strong, W. B., Malina, R. M., Blimkie, C. J., Daniels, S. R., Dishman, R. K., Gutin, B.,

Hergenroeder, A. C., Must, A., Nixon, P. A., Pivarnik, J. M., Rowland, T., Trost, S., & Trudeau, F. (2005) Evidence-based physical activity for school-age youth. The Journal of Pediatrics, 146, 732-737.

Tabachnick, T. B., & Fidell, L. (2007) Using multivariate statistics. (5th ed.) Boston, MA: Allyn & Bacon.

Toussaint, L., & Friedman, P. (2009) Forgiveness, gratitude, and well-being: the medi-ating role of affect and beliefs. Journal of Happiness Studies, 10, 635-654. Published online 12 August, 2008, Springer Science+Business Media B.V. DOI: 10.1007/s10902-008-9111-8.

Trost, S. G., Pate, R. R., Sallis, J. F., Freedson, P. S., Taylor, W. C., Dowda, M., & Sirard, J. (2002) Age and gender differences in objectively measured physical activity in youth. Medicine & Science in Sports & exercise, 34, 350-355.

Veenhoven, R. (2003) Happiness. The Psychologist, 16, 128-129.Vittersø, J., Oelman, H. I., & Wang, A. L. (2007) Life satisfaction is not a balanced

estimator of the good life: evidence from reaction time measures and self-reported emotions. Journal of Happiness Studies, 10, 1-17.

Wessman, A. E., & Ricks, D. F. (1966) Mood and personality. New York: Holt, Rinehart and Winston.

accepted September 21, 2011.