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Physical activity and depressive symptoms in rural adolescents.
Abstract:
Physical activity participation and its effect on mood are not well understood in rural adolescents. Data collected from 852 9th and 10th graders (age in years: M = 14.8, SE = 0.02) in three northwestern U.S. public high schools were analyzed to determine physical activity and physical education (PE) class participation, and to examine the relationship between physical activity and mood. A significantly lower proportion of females compared to males reported participating in a daily PE class and exercising vigorously. Controlling for health status, gender, and school, vigorous exercise was significantly associated with a lower score on Children's Depression Inventory. The results of this study highlight the need for additional research on factors affecting physical activity participation in rural students, particularly females.

Article Type:
Report
Subject:
Exercise (Health aspects)
Exercise (Demographic aspects)
Depression, Mental (Care and treatment)
Depression, Mental (Prevention)
Depression, Mental (Research)
Rural youth (Psychological aspects)
Rural youth (Physiological aspects)
Rural youth (Demographic aspects)
Authors:
Prasad, Aman
St-Hilaire, Sophie
Wong, Maria M.
Peterson, Teri
Loftin, John
Pub Date:
03/01/2009
Publication:
Name: North American Journal of Psychology Publisher: North American Journal of Psychology Audience: Academic Format: Magazine/Journal Subject: Education; Psychology and mental health Copyright: COPYRIGHT 2009 North American Journal of Psychology ISSN: 1527-7143
Issue:
Date: March, 2009 Source Volume: 11 Source Issue: 1
Topic:
Event Code: 310 Science & research
Geographic:
Geographic Scope: United States Geographic Code: 1USA United States
Accession Number:
195427678
Full Text:
More than one third of American teenagers today do not partake in daily physical activity (National Center for Health Statistics, 2005; Paluska & Schwenk, 2000). Furthermore, adolescent participation in vigorous physical activity (defined by the CDC as physical activity for at least 20 minutes on 3 or more days per week that induces sweating and heavy breathing) declined over a ten-year period from 1993 to 2003 (Adams, 2006). In addition, adolescent participation in physical education (PE) classes (a potentially significant source of regular exercise for adolescents in the United States) dropped substantially from 42% to 28% between 1991 and 2003 (Centers for Disease Control and Prevention, 2006). These trends are concerning, since adolescence is an important period for establishing life-long physical activity patterns (Telama et al., 2005).

Physical inactivity accounts for 3.9% of worldwide deaths annually, and accounts for a larger proportion of the disease burden in developed countries such as the United States (Murray & Lopez, 1996). For young people, increased rates of non-communicable diseases, including a doubling in the number of overweight adolescents in the past 20 years, are due in large part to sedentary lifestyles (Centers for Disease Control and Prevention, 2006; Council on Sports Medicine and Fitness, 2006). Regular physical activity is a critical component of a healthy lifestyle in adolescents because it can prevent the onset of serious medical conditions including cardiovascular disease, obesity, hypertension, and type 2 diabetes (Dehghan, Akhtar-Danesh, & Merchant, 2005; Penedo & Dahn, 2005). In addition, regular physical activity may be important to psychological well-being. A significant amount of data suggest that physical activity is inversely related to depressive symptoms and may help to mitigate the negative effects of mood disorders in adolescents and adults (Paluska & Schwenk, 2000; Yeung, 1996).

The World Health Organization estimates that mood disorders are the second largest contributor to the global disease burden behind cardiovascular conditions (National Institute of Mental Health, 2001). Depression, currently the fourth leading cause of loss of productive life-years globally, is expected to be the second leading cause by 2020, surpassing tuberculosis, malaria, war, and HIV (Murray & Lopez, 1996). Kessler and Walters (1998) estimate that 33% of females and 20% of males age 15 to 24 years in the United States have been depressed at some point in their lives and suggest the problem is growing. Data from recent birth cohorts indicates that the prevalence of depression is highest among adolescents age 15 to 24 years declining monotonically with age (Cross-National Collaborative Group, 1992). Depression is occurring earlier than ever before in the United States (Cross-National Collaborative Group, 1992).

Participation in physical activity and the associated effects on mood are not well understood in rural adolescent populations. Physical inactivity, however, is an acute problem among rural adult populations and rural adolescents are at greater risk for psychological disorders (Parks, Housemann, & Brownson, 2003; Peden, Reed, & Rayens, 2005). We know of only one published study that provides information on the physical activity and PE class participation of rural adolescents (Springer, Hoelscher, & Kelder, 2006). The study analyzed nationally representative data from the Center of Disease Control Data Youth Risk Behavior Survey in 2003. Results indicated that youth living in the southern United States and in urban settings had lower physical activity participation rates compared to youth in the western United States and in rural settings.

There is also a lack of published studies on the effect of physical activity on depressive symptoms in adolescents (Motl, Birnbaum, Kubik, & Dishman, 2004). Only 2 published studies on this association used non-clinically depressed samples and controlled for known confounders, including socioeconomic status (SES) and some measure of general health (Motl et al., 2004; Steptoe & Butler, 1996). One study employed a longitudinal design and found that naturally occurring changes in physical activity were negatively related to changes in depression scores among 4,594 U.S. adolescents over a 2-year period (Motl et al., 2004). The relation remained significant when the effect of confounding variables such as gender and socioeconomic status was controlled for. Another study found a positive relation between an index of sport and vigorous activity and psychological well-being among 5,061 adolescents in the United Kingdom, independent of the effect of gender, social class, health status and use of hospital service (Steptoe & Butler, 1996). To date, no studies of the association between physical activity and depressive symptoms have studied adolescents in U.S. rural settings. The limited studies on the exercise pattern and mood disposition of rural adolescents suggest that more empirical research on this topic is necessary.

The objectives of the present study were to 1) determine the percentage of students in a medium-sized town (population 50,723) in rural northwestern U.S. who exercised at or above the CDC recommended level for adolescents; 2) report the percentage of students who achieved this level of exercise through public high school PE classes; and 3) confirm or refute the presumptive correlation between exercise and mood state in a normative population of 9th and 10th grade high school students adjusting for SES, self-reported health status, grade, age, gender, and race.

METHOD

Participants

Participants were 852 9th and 10th grade students from three public high schools located in a rural area in northwestern U.S. The students' average age was 14.8 years (SE = 0.024). Eighty-five percent of the sample consisted of Caucasian students, 2.0% consisted of Native American students, 0.85% consisted of African-American students, 2.0% consisted of Asian Pacific Islander students, 3.5% consisted of Hispanic students, and 6.7% described their race as 'other.' These proportions are within 1.5% of the estimated proportions of Caucasian, Native American, African-American, Asian Pacific Islander, and Hispanic youths between the ages of 10 and 19 in the county where the study took place (US Census Bureau, 2004). Almost half (49.6%) of the participants were freshmen (n = 423). Fifty-seven percent (57%) of participants surveyed were female (n = 485).

All 9th and 10th grade students from the three high schools were invited to participate. Parental consent and student assent were obtained. The survey response rate was 47%. Twenty-four surveys (2.7%) were excluded from the analysis due to incomplete data.

Zip code was used to classify the socio-economic status of participants. Based on zip code, 52.1% of participants lived in an area with a 'medium' median household income ([micro] =$37,197), 25.5% lived in an area with a 'high' median household income ([micro] = $42,403), and 22.4% lived in an area with a 'low' median household income ([micro] = $27,547).

Instrument

A 23-item questionnaire was designed to assess the physical activity habits, mood, basic demographic information, and general health state of 9th and 10th grade high school students. The first ten items of the instrument comprised the Children's Depression Inventory Short-Form (CDI-S;Kovacs, 1985). The CDI-S measures depressive symptoms in children and adolescents ages 7 to 17 years. CDI-S raw scores range from 0 to 20. Previous research suggests that the CDI-S is psychometrically sound, with high internal consistency (Kovacs, 1992; Mather & Cartwright-Hatton, 2004). In a non-clinical sample, test-retest reliability coefficients for the CDI-S were acceptable, ranging from 0.74 to 0.77 (Smucker, Craighead, Craighead, & Bean, 1986). Results from the CDI-S have been shown to be comparable to the 27-item long-form CDI from which it is derived (Kovacs, 1992). The CDI long-form has shown good test-retest reliability, high concurrent validity, and high internal consistency in clinical and non-clinical samples (Brooks & Kutcher, 2001). In this study the Cronbach's alpha coefficient for the CDI-S items was 0.84.

Four multiple-choice questions from the Center for Disease Control 2005 Youth Risk Behavior Survey (CDC YRBS) were used to assess the level of vigorous and moderate physical activity of the students in the last seven days and over the last 3 months (Gunbaum et al., 2004). The definitions for vigorous and moderate physical activity used in this study are based on national guidelines provided by the CDC (Gunbaum et al., 2004). A single multiple-choice question from the YRBS was used to assess participation in a PE class ("In an average week when you are in school, on how many days do you go to physical education (PE) classes?") The test-retest reliability for the nationally administered YRBS as a self-report measure has been well established. Previous research has shown that the YRBS physical activity items used in this study, including the item on PE class participation, have excellent test-retest reliability (Brener, Collins, Kann, Warren, & Williams, 1995; Brener, et al., 2002;

Lowry, Wechsler, Kann, & Collins, 2001). In addition, previous research suggests the YRBS definitions of vigorous and moderate physical activity correlate well with physiological indicators of fitness, suggesting construct validity (Prochaska, Sallis, Sarkin, & Calfas, 2000). In adolescents, the YRBS question on vigorous physical activity has been shown to be highly correlated with actual vigorous exercise as measured by an accelerometer even when the question is administered independent of the other YRBS questions (Troped, et al., 2004). Overall, self-reported physical activity levels by adolescents appear to be reliable (Sallis, 1991).

Two multiple-choice questions modified from a previous study on the association between physical activity and mood in adolescents were used to assess the general health status of the students (Steptoe & Butler, 1996). The first item asked respondents, "How many times in the last 3 months have you been sick, injured, or felt sick for a period of at least 2 days where your regular routine was interrupted?" The second item asked respondents, "How many times in the last 3 months have you been to the doctor's office, hospital, or any other medical facility because you were unwell, sick, or injured?" Three open-ended items (grade, age, and zip code) and two multiple-choice items (gender and race) asked for respondents' demographic information. The final question asked for respondents' weight and height and was open-ended.

Procedure

The principal investigator administered the survey in each classroom using a standardized script of instructions and procedures. Students had access to a tape measure and scale at all three high schools to obtain their weight and height if necessary.

The proportion of males and females that exercised vigorously at or above the CDC recommended level was compared using a logistic regression analysis controlling for school, grade, race, SES, and the interaction term gender by grade. Due to the low ethnic diversity in our population the race of the participants was categorized as Caucasian or 'other', and this dichotomous variable was included in the model. The proportion of males and females enrolled in daily PE classes was also compared with the same variables using a logistic regression analysis. Only variables with p values less than .05 were considered significant and maintained in each model. The Hosmer-Lemeshow Chi-Square test was used to evaluate each model's goodness-of fit.

The relationship between physical activity and CDI-S raw score was evaluated using a multiple regression model. The response variable was the CDI-S raw score. Physical activity and health were treated as continuous variables. For highly correlated variables (i.e. the physical activity questions and the health questions) only one variable was included in the model. As a result, moderate physical activity participation was described for the sample but excluded from the analysis. Other variables included in the model were school, gender, race, grade, and socioeconomic group. All possible two-way interaction terms were initially included in the model.

RESULTS

Vigorous physical activity participation

On average, males and females exercised vigorously for 4.27 (SE = 0.126) and 3.34 (SE = 0.102) days per week, respectively (Table 1). 74% of males and 60% of females reported exercising vigorously three or more days in a week. 54.2% of female 10th graders and 74.7% of male 10th graders met the CDC recommended level of exercise (Table 2).

Logistic regression analysis showed that only gender and grade level were associated with adequate weekly vigorous exercise. Female 10th grade students exercised the least (see Table 2). After controlling for grade, the odds of males exercising at the CDC recommended level was, on average, 1.88 times greater than for females (OR = 1.88, 95% CI = 1.40 - 2.53, Wald [chi square] = 4.17, p < .001). Ninth-grade students were 1.35 times more likely to meet the recommended exercise level compared to 10th grade students after controlling for the gender effect (OR = 1.35, 95% CI = 1.01 - 1.82, Wald [chi square] = -2.05, p < .05). The proportion of students that exercised at the CDC recommended level was not significantly related to school, race, or SES. The Hosmer-Lemshow statistic ([chi square] = 3.7, p = 0.15) indicated the logistic regression model fit the data adequately.

PE class participation

Sixty-six percent of all students surveyed did not take a daily PE class. Only 19.2% of females surveyed were enrolled in a daily PE class compared to 45.8% of the males surveyed. Only 16.7% of 9th grade females were enrolled in a daily PE class (Table 2). In contrast, 41.3% of 9th grade males had a daily PE class.

Logistic regression analyses showed that race, grade, and gender were all associated with enrollment in PE classes. After controlling for grade and race, the odds of males being enrolled in a PE class was, on average, 3.69 times greater than for females (Wald [chi square] = 8.28, p < .01). Other factors that affected the probability of enrollment in a PE class were grade level (Wald [chi square] = 2.24, p < .05) and race (Wald [chi square] = 2.20, p < .05). Ninth-grade students were, on average, 1.42 (95% CI = 1.05, 1.93) times more likely to be enrolled in PE than 10th grade students. Caucasian students were, on average, 1.60 (95% CI = 1.05, 2.43) times more likely to enroll in PE compared to other races, controlling for gender. The proportion of students taking a daily PE class did not differ significantly by school or SES. The Hosmer-Lemeshow statistic ([chi square] = 0.604, p = 0.896) indicated the logistic regression model fit the data adequately.

Health status

Seventy-five percent of the students reported being sick three or fewer times in the past three months. The mean number of interruptive events of illness in the past 3 months was 2.29 (SE = 0.082) for females and 1.56 (SE = 0.082) for males (see Table 1). The median value for interruptive events of illness was between 1 and 3 events at all three high schools.

Correlations were calculated among health status and physical activity variables. Significant correlations were found among the following variables: vigorous exercise completed over a week and vigorous exercise completed over three months (r = .733, p < .01); moderate exercise completed over seven days and over three months (r = .649, p < .01); and events of illness over three months and clinic visits over three months (r = .452, p < .01).

Depressive Symptoms (CDI-S scores)

CDI-S raw scores range from 0 to 20. The mean depression score for all respondents in this study was 2.81 (SE = 0.111) (Table 1). Overall, 75% of CDI-S scores were below 4.00. The proportion of participants scoring above the suggested clinical cutoff of eight points was 9.8% (Schneider-Jamner, Spruijt-Metz, Bassin, & Cooper, 2004). The mean raw score was 2.89 for females (SE = 0.14) and 2.69 (SE = 0.18) for males.

The multiple regression model used to explain variation in the CDI-S depression score included the following variables: gender, school, events of illness in the past three months, days of vigorous physical activity in a week, and the interaction terms school by events of illness, school by days of vigorous physical activity, and school by gender. This model accounted for approximately 27% of the variation in the mood score of students ([F.sub.11,839] = 29.5, p < .001) (see Table 3). SES, grade level, race, and all other two way interaction terms were not significant.

Each day of vigorous physical activity was inversely related to mood. This relationship was not different between two of the high schools, but had a significantly lower slope at the third high school (see Table 3). At two of the three schools, females had lower mood scores than males after adjusting for health status and physical activity. At the third school, however, there was no difference between males and females ([beta] = 0.04, p = 0.90). The number of events of illness was positively associated with mood scores at all three schools after controlling for gender and physical activity ([F.sub.1,839] = 140.65, p < .001); however, the relationship between health events and mood was significantly different for the different schools (F2,839= 6.13, p < .001).

DISCUSSION

Approximately thirty-four percent (33.8%) of the participants did not meet the CDC weekly recommended level for vigorous exercise of 20 minutes per day for at least 3 days in a week at the time of the survey. Of the 66.2% of individuals that did meet the recommended level, only 43.1% were enrolled in a PE class at their high school (also see Table 2). The percentage of students taking part in some form of physical activity and the overall percentage of students enrolled in a PE class in this study were consistent with data collected at the national and state level for the 2003 YRBS (Grunbaum et al., 2004; Idaho Department of Education, 2003).

Males were more likely than females to exercise vigorously and participate in daily PE in this study, a finding consistent with previous studies in rural and non-rural adolescents (Gordon-Larsen, McMurray, & Popkin, 2000; Springer et al., 2006). Ninth graders were more likely than 10th graders to exercise vigorously and participate in daily PE. Data from one recent study suggests older adolescents are less likely to participate in all forms of physical activity than their younger peers (Gordon-Larsen et al., 2000). Our results may be a manifestation of this trend. It appears that adolescent choices on physical activity participation are correlated with a number of interrelated psychosocial factors such as self-efficacy (i.e., confidence in one's ability to be physically active) and influences of family and friends on physical activity (Strauss, Rodzilsky, Burack, & Colin, 2001). These factors may explain the developmental differences reported here.

Additionally, the differences between the two grade levels may be due to differences in curriculum requirements. For instance, schools may require students in higher-grade levels to devote more time to academic work. To the best of our knowledge, the requirements for both grade levels were very similar in all three schools we studied. A systematic analysis of curriculum requirements and psychosocial factors associated with physical activity is beyond the scope of this study. However, such information is very important for future studies focusing on developmental differences in physical exercise.

Exercise patterns developed during adolescence often carry over into adulthood, highlighting the importance of introducing young people to regular physical activity (Telama et al., 2005). Participation in free PE classes in the public school system is one way to ensure that young people achieve the recommended level of exercise regardless of their socioeconomic status, and perhaps develop a liking for physical activity that remains with them later in life. The results of this study suggest that certain groups of rural adolescents (females, 10th grade students, and nonCaucasian students) are not enrolling in PE in numbers equal to their peers. Particular attention should be given to female participation since physical activity interventions administered through PE classes have shown promise in increasing physical activity participation rates in females (Schneider-Jamner, Spruijt-Metz, Bassin, & Cooper, 2004). The percentage of females enrolled in a PE class in this study was surprisingly low (19.2%), especially for 9th graders (16.7%).

Of the females that exercised at or above the CDC recommended level for vigorous exercise, only 27.7% were enrolled in PE, compared to 59.6% of males. This suggests that more female students achieve the CDC recommended activity level by exercising outside of school compared to male students. This finding suggests that females of lower socioeconomic groups, who may not be financially able to enroll in extracurricular activities outside of the school curriculum, may be at a disadvantage for meeting the CDC recommended level of exercise. A trend suggesting fewer of the females in the lower socioeconomic group met the CDC recommended level of exercise was observed in this study. However, this difference was not statistically significant when gender and grade level were included in the logistic regression model, and this socioeconomic disparity was not apparent in the male students.

The lack of a relationship between SES and exercise in this study may have been due to the method we used to classify the socioeconomic status of individuals. The zip-code data we used probably does not capture true SES well in a medium-sized town. A more thorough investigation into the relationship between SES and exercise in female adolescents is critical, given the low enrollment of females in free PE classes in this study, and findings from other studies that suggest adolescents from lower socioeconomic backgrounds have significantly higher rates of physical inactivity compared to wealthier individuals (Gordon-Larsen et al., 2000).

Among the physical benefits of exercise, several studies have demonstrated a positive association between physical activity and mood in adolescents (Motl et al., 2004; Steptoe & Butler, 1996). To the best of our knowledge, this is the first study to corroborate this association in a rural sample of non-clinically depressed adolescents. Although a cross-sectional study design was used to collect data on the level of physical activity and mood of the students, thus limiting the causal interpretation of the relationships detected in the study, the data of this study corroborates the previously published association between activity and mood. Individuals who exercised more had lower scores on the depression index. Most students in this study (90.2%) had mood scores within the normative range; however, those who exercised regularly had moderately lower scores on the CDI-S, indicating a lower tendency for depressive symptoms, a finding consistent with other studies (Allison et al., 2005; Delahanty, Conroy, & Nathan, 2006; Yeung, 1996). Also consistent with previous studies were the findings that only vigorous exercise was associated with mood and that a greater number of interruptive events of illness was correlated positively with mood scores that reflected increased depression (Steptoe & Butler, 1996).

Interestingly, the mean raw mood score for females was not statistically different from males (Table 1). However, after adjusting for health events, school, and physical activity, females had, on average, lower depression scores than males. The relationship between mood and exercise among females highlights another reason to further investigate the low level of exercise in females reported in this study. Replication of the current finding is necessary. More data on physical health, physical activity, academic curriculum and mental health status of adolescents may help us understand the possible gender differences on the relations between mood and exercise.

The response rate in this study was only 47%, and proportionately more females participated in the survey. Although response bias from students refusing to participate may have skewed the results of this study, it is unlikely that it had a large effect, given that the level of activity reported by the students and the mean CDI-S scores were consistent with other surveys and with national averages (see Tables 1 and 2) (Gunbaum et al., 2004; Kovacs et al., 2003). Furthermore, the PE class participation of 9th and 10th grade students reported in this study was within 5% of the actual 2005 school district enrollment rates for females and within 3% for males, suggesting the sub-sample of students was representative of the school population.

Although self-reported levels of physical activity and mood are reliable, they can be biased by a number of factors, including the setting in which the survey was administered and culturally acceptable perceptions of physical activity and depression (Sallis, 1991). Respondents may have overestimated the amount of time they participated in physical activity. To determine the consistency of responses provided by the students, correlations between 7 day and 3 month vigorous and moderate physical activity questions and between the two health status items were obtained and were significant. Internal consistency for the 10 CDI-S items as determined by a Cronbach's alpha coefficient was high (.80) and consistent with the range of alpha coefficients (.71 to .89) obtained in previous research with the CDI-S (Kovacs et al., 2003).

Health status in our analysis was determined by one self-reported item measuring the number of events of illness. The reliability and validity of this item is unknown. However, the finding that events of illness were significantly associated with increased depression scores was consistent with previous research (Steptoe & Butler, 1996). Further, as with the similar physical activity variables, the two health status items were significantly correlated. All of these findings indicated that students responded consistently on similar questions. Furthermore, of the individuals that claimed to attend a PE class, 92.7% claimed to exercise vigorously at least three days per week over the last three months. The latter suggests that students were consistent in responding to the exercise questions on the survey.

Finally, the small number of items used to measure physical activity and illness is another limitation of the study. Although we believe the items are good measures of the variables that we are interested in, future studies should include a larger number of items, if possible.

In summary, 26.9% of our respondents reported no participation in adequate vigorous or moderate physical activity. Of particular concern, rural female adolescents reported significantly lower levels of vigorous physical activity and lower daily PE class participation compared to males. Females also had, on average, higher scores on the depression index, which appeared to be due, in part, to lower exercise levels. High school curricula that encourage physical activity programs and PE classes (both during and outside of school hours) might benefit the physical and psychological well being of adolescents.

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Acknowledgements: We would like to thank all participating students as well as the faculty and staff from each of the three participating high schools for their willingness to engage in the study. We would also like to thank the administrators of the school district for their cooperation. This project was supported by a faculty start-up grant awarded to Dr. Sophie St.-Hilaire from the Office of Research at Idaho State University and a faculty research grant awarded to Dr. Maria Wong from the WeLEAD program at Idaho State University.

Aman Prasad

Cornell University

Sophie St-Hilaire, Maria M. Wong, and Teri Peterson

Idaho State University

John Loftin

Century High School

Author info: Correspondence should be sent to: Maria Wong, Ph.D., Dept. of Psychology, Idaho State U., Stop 8112, Pocatello, ID 83209.
TABLE 1 Mean Values for Selected Variables

                        Overall        Male            Female

                        M (SE)         M (SE)          M (SE)

Age                     14.81 (0.024)  14.84 (0.038)   14.79 (0.031)

CDI-S score             2.81 (0.111)   2.69 (0.183)    2.89 (0.138)

Vigorous PA (a)         3.74 (0.081)   4.27 (0.126)    3.34 (0.102) ***

Moderate PA (b)         3.29 (0.073)   3.32 (0.111)    3.27 (0.095)

Events of illness (c)   1.98 (0.059)   1.56 (0.082)    2.29 (0.082) ***

Abbreviations: PA, physical activity; M, mean.

(a) Physical activity for at least 20 min that made them sweat/
breathe hard on 3 or more of past 7 days. (b) Physical activity for
at least 30 min that did make them sweat or breathe hard for at
least 30 min on 5 or more of past 7 days. (c) Events of illness in
past 3 months for at least 2 days that interrupted their regular
routine.

*** Independent samples t-tests comparing male and female showed
that the two groups were significantly different on vigorous
physical activities (t(850)= 5.76, p < .001) and events of illness
(t(849)= 6.17, p < .001). The two groups were not significantly
different on age (t(850)= 1.19, p = .23), CDI-S scores (t(850)=
.91, p = .36) and moderate physical activity (t(850)= 0.28, p =
.78).

TABLE 2 Percentage of Students Participating in Various Physical
Activity Related Behaviors at CDC Recommended Amounts

                              Male                Female

                    9th Grade      10th Grade     9th Grade

Vigorous PA (c)     73.5           74.7           66.7

Moderate PA (d)     38.1           36             30.8

Daily PE (e)        41.3           50.6           16.7

Daily PE and        39.15          49.4           15
vigorous PA (f)

                    Female         Idaho (a)      U.S. (b)

                    10th Grade
Vigorous PA (c)
                    54.2           66.4           64.6
Moderate PA (d)
                    36.3           29.5           25.5
Daily PE (e)
                    21.5           29.5           32.2
Daily PE and
vigorous PA (f)     18.3           -- (g)         41.9

Abbreviations: PA, physical activity; PE, physical education class.

(a) Data reference: Idaho Department of Education, 2003. (b) Data
reference: Centers for Disease Control, 2004. (c) Physical activity
for at least 20 min that made them sweat breathe hard on 3 or more
of past 7 d. (d) Physical activity for at least 30 min that did make
them sweat or breathe hard for at least 30 min on 5 or more of past
7 d. (e) Enrolled in a daily physical education class. (f) Enrolled in a
daily physical education class and vigorous physical activity on 3
or more of past 7 d. (g) This proportion was not available for Idaho
data.

TABLE 3 Parameter Estimates for Significant Variables in the
Regression Model

Parameter                    B         SE            T

                           -.588       .073      -8.029 **
Vigorous PA (a)
                           .928        .094      9.928 **
Events of illness (b)
                          -1.965       .574      -3.421 **
School = C
                           -.021       .663        -.031
School = H                 .039        .323        .121
School C*Female           -1.001       .389      -2.570 **
School H*Female           -1.054       .338      -3.116 **
School P*Female            .412        .098      4.199 **
School C*Vig PA (a)
                           .087        .107        .806
School H*Vig PA (a)        -.246       .131       -1.881
School C*illness (b)
                           -.506       .145      -3.487 **
School H*illness (b)

Note. Dependent variable is total CDI-S mood score. Adjusted
[R.sup.2] = 0.27. Abbreviations: PA, physical activity; [beta], beta
coefficient of association. (a) Physical activity for at least 20
min that made them sweat breathe hard on 3 or more of past 7 d. (b)
Events of illness in past 3 months for at least 2 days that
interrupted their regular routine. (c) This parameter is set to 0
because it is redundant. ** p < 0.01
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