Evidence Review

The Relationship Between Physical Activity and Depressive Symptoms in Adolescents: A Systematic Review Patricia Bursnall, RN, MA

ABSTRACT Keywords adolescents, physical activity, depression/ depressive symptoms

Background and Purpose: Depression affects a significant number of adolescents and requires creative treatment planning. Physical activity (PA) as a treatment option for depression has moderate support through repeated systematic reviews in adults, but not in adolescents. The purpose of this work is to present a systematic review of the evidence within the past 5 years regarding the relationship between PA and depressive symptoms (DS) in adolescents, and to determine if the evidence supports PA as a viable treatment option for this age group. Methods: An extensive search was conducted through MEDLINE (i.e., Ovid and PubMed), CINAHL, and PsycINFO databases. Ten primary articles were ultimately selected and reviewed for their quality and contributions to the subject. The SORT tool was utilized to grade individual works and the body of evidence as a whole. Findings: As of the writing of this review, the author finds only one randomized controlled trial that explores the interaction between PA and DS in the adolescent age group. However, the body of evidence generated from this review indicates a strong inverse correlation between the two variables. Linking Evidence to Action: Further research must be conducted to determine causation. However, healthcare providers can and must provide both health education and health promotion surrounding the relationship between PA and DS in the adolescent age group to enhance wellness and prevent disease.

INTRODUCTION Depression is an insidious disease currently affecting 350 million people worldwide (World Health Organization [WHO], 2012). On any given day in the United States, nearly 8% of adolescents report current depression (Centers for Disease Control and Prevention [CDC]: National Center for Health Statistics, 2013). Adolescence is an emotionally labile time of life, with the majority of first-time depression diagnoses occurring just after the teen years (Stavrakakis, de Jonge, Ormel, & Oldehinkel, 2012). Therefore, prevention and treatment of subclinical and diagnosed depression in adolescents demands attention and clear guidelines for healthcare providers. The purpose of this study was to perform a systematic review of the research that has evaluated the impact of physical activity (PA) on depressive symptoms (DS) in adolescents, and to determine if the strength of the evidence might support PA as a complementary approach to combat DS in adolescents. The following is a critical analysis of this issue and the primary quantitative research involving the relationship between PA and DS in adolescents. The research is summarized and graded on the strength of its evidence using the Strength of

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Recommendation Taxonomy or SORT tool (Ebell et al., 2004) and recommendations made for primary care providers.

PICO QUESTION The development of the clinical question in PICOT format (P = patient population; I = intervention of interest; C = comparison intervention; O = outcomes; T = time if applicable) drives the provider to think critically about the population under study, and provides a focus for the identification of related research (LoBiondo-Wood & Haber, 2010; Melnyk & FineoutOverholt, 2011). Though a significant body of evidence exists on the topic of PA as adjuvant treatment of depression in adults (Rimer et al., 2012), the relationship between these two variables in the adolescent population is not as well or as recently documented (Biddle & Asare, 2011). The PICO question for this study was: In adolescents (P), how does PA (I) compared to no PA (C) significantly reduce DS (O)? Adolescence is the population in this clinical question. Adolescence is defined in growth and development circles as the period of youth between the chronological ages of 11–17 (Burns, Dunn, Brady, Starr, & Blosser, 2013). This age group is of

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Evidence Review particular interest because they are often perceived by providers as apathetic to preventive counseling during a primary care visit (Ham & Allen, 2012). Therefore, Ham and Allen (2012) note that adolescents often receive less anticipatory guidance, even though both teens and their parents would prefer that providers offer increased guidance at this age. PA or lack of PA is the intervention and comparison in this clinical question, respectively. This review uses the CDC definition of PA, which states that it is, “Activity in which the body’s large muscles move in a rhythmic manner for a sustained period of time” (CDC: Division of Nutrition, Physical Activity, and Obesity, National Center for Chronic Disease Prevention and Health Promotion, 2011, para. 2). The CDC (2013) notes that recommended PA for children and adolescents is a minimum of 60 minutes per day. For the purposes of this analysis, it is important to note that each individual study looks at different duration or intensity of PA, and compares it to guidelines that may or may not be applicable in this country. The measurement of PA is accomplished in a variety of ways in research, including self-report, direct observation, and actigraphy. Actigraphy utilizes electronic accelerometer technology to record gross motor movements, which allows it to record a wider variety of PA than the pedometer (Dopp, Mooney, Armitage, & King, 2012). A change in DS is the outcome data for this clinical question. Depression is defined in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-V-TR) in terms of different disorders. According to the DSM-V-TR (American Psychiatric Association, 2013), criteria for a major depressive disorder comprises a minimum of five symptoms for over 2 weeks from a comprehensive list including, but not limited to: anhedonia, fatigue, hypersomnia or insomnia, weight loss or gain, and depressed mood or irritability in youth. Different self-report measures (e.g., Children’s Depression Rating Scale, Dopp et al., 2012; Depression Self-Rating Scale for Children, Cao et al., 2011; Patient Health Questionnaire-9 Modified for Adolescents, Ham & Allen, 2012) given to individuals measure these symptoms and are tested for validity and reliability in diagnosing depression. Although these inventories are only one portion of the clinical diagnosis of depression, a self-report measure gives an indication of the placement of that individual along a spectrum of depressed to nondepressed thinking (i.e., DS). In this analysis, it was imperative to analyze each depression measurement tool to determine if it is valid and reliable.

SIGNIFICANCE OF THE PROBLEM Depression is the leading cause of disability and accounts for 1,000,000 deaths from suicide each year, globally (WHO, 2012). The CDC (2013) reported that suicide remains the third leading cause of death in the 15–24 years age group, and the sixth leading cause of death in the 5–14 years age group. Lynch and Clark (2006) reported that before age 18, it is estimated that 20% of adolescents will experience an episode of depression. According to a systematic review of the economic burden Worldviews on Evidence-Based Nursing, 2014; 11:6, 376–382.  C 2014 Sigma Theta Tau International

of depression in youth by Lynch and Clark (2006), the cost of depression in children and adolescents is difficult to estimate as this population often receives services outside of the healthcare system. However, the authors also report that a study by Mandell, Guevara, Rostain, and Hadley (as cited in Lynch & Clark, 2006) found that depression in youth contributed to a nearly US$7,000 increase in healthcare costs per individual over a period of 3 years. Lynch and Clark (2006) found some promise in the cost-effectiveness of treatment of depression in youth, with cognitive behavioral therapy showing the most promise at $10 per depression-free day. Adequate depression treatment is multifaceted and, in adults, often involves the use of expensive antidepressant medication and psychotherapy (Rimer et al., 2012). Unlike adults, treatment for depressed adolescents does not include antidepressant medications as a first-line treatment (WHO, 2012). According to the WHO (2012), antidepressant medications can contribute to increased suicidal ideation, and have been attributed to completed suicides in youth. A black-box warning was issued for antidepressants in 2005. With the black-box medication warnings for antidepressant use in adolescents, providers and parents are looking for alternative ways to assist depressed youth (Dopp et al., 2012). PA, as a natural and inexpensive way to assist in decreasing DS, has received more attention in adults with positive results (Rimer et al., 2012). Rimer and colleagues (2012) indicate that exercise can be recommended to depressed adults as part of a comprehensive and individualized plan. PA as an intervention for depression in youth has gained interest in the past 20 years (Biddle & Asare, 2011). However, the evidence for PA as a means for decreasing DS in adolescents remains unclear (Biddle & Asare, 2011; Dunn & Weintraub, 2008).

METHODS A thorough literature search was conducted via online and bibliographic sources for original, published research on the topic using the MEDLINE (i.e., Ovid and PubMed), CINAHL, and PsycINFO databases in July 2013. Search terms included PA or exercise, adolescents, adolescence or youth, and depression or DS. Initial selection criteria included English language and publication from 2008 to the present. Exclusion criteria included non-English language, publication prior to 2008, not primary research, or a topic that did not include all PICO question attributes (i.e., wrong age group, incomplete gender sampling, wrong mental disorder, sports groups vs. PA measurement). Although two systematic reviews are available for this topic, the selection of only primary research is preferred to gather the most up-to-date research. Therefore, the reviews are utilized as a source of information rather than a direct inclusion. This review contains 10 primary research articles that meet inclusion criteria: eight are large, nonexperimental cohort studies, one is a randomized controlled trial (RCT), and one is a trial without randomization or control (see Figure 1). The

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467 articles containing physical activity or exercise AND depression or depressive symptoms AND adolescents, adolescence or youth identified through: ● ● ● ●

MEDLINE (Ovid and PubMed) = 256 CINAHL = 126 PsycINFO = 85 Bibliographic review = 1

221 articles excluded for: ● ●

Before 2008

Non-English language

62 articles excluded as repeats

246 articles

184 titles or abstracts reviewed

174 articles excluded for: Inappropriate ● population (i.e., not adolescents, only boys or only girls) = 40 ● Off-topic, different mental disorder = 132 ● Not primary research = 2

10 articles included in review: ● ● ●

8 nonexperimental cohort studies 1 RCT 1 trial without randomization or control

Figure 1. Process for article inclusion. articles were reviewed by one researcher and considered for their design, data analysis, results, and implications, and graded according to the SORT tool, which classifies individual research on a 1–3 level of evidence system, with an overall strength of recommendation grade of A–C (Ebell et al., 2004). It is important to note that according to the SORT tool, level 1 evidence includes a high-quality RCT with an appropriate size and follow-up, blinding if possible, allocation concealed, and intention-to-treat analysis, or a high-quality diagnostic or prognosis cohort study with adequate follow-up (Ebell et al., 2004). Level 2 evidence might include prevention, treatment,

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or screening cohort studies, a lower quality clinical trial, or a case-control study (Ebell et al., 2004). Level 3 evidence might include consensus guidelines, opinion, or usual practice (Ebell et al., 2004). All studies identified for this review are either level 1 or 2 evidence (Table 1).

FINDINGS This systematic review considers research regarding PA and DS from over 25,000 adolescents from a variety of cultures (e.g., Chinese, Canadian, Australian, American, English, Dutch, and Worldviews on Evidence-Based Nursing, 2014; 11:6, 376–382.  C 2014 Sigma Theta Tau International

Evidence Review Table 1. Brief Summary of Evidence

Citation of evidence

Study design

Findings

Recommendationsimplications level of evidence SORT tool (Ebell et al., 2004)

Cao et al. (2011) Hong et al. (2009) Kremer et al. (2013) Wiles et al. (2012)

Large, nonexperimental cohort design Mean age across studies = 13.0

• Significant, consistent inverse relationship between PA and DS • Inconsistent results regarding additive negative effect of increased screen time on DS (Cao et al., 2011; Kremer et al., 2013)

• Future research must be designed to establish causality • Exercise recommendations must be promoted more rigorously • All studies level 2

Rothon et al. (2010) Shields et al. (2010) Stavrakakis et al. (2012) Sund et al. (2011)

Large, nonexperimental longitudinal design Mean age at first measurement across studies = 12.5

• Significant, consistent inverse relationship between PA and DS over time, with two studies establishing a >80% follow-up • Bidirectional relationship between PA and DS (Stavrakakis et al. 2012) • At mean level self-efficacy, no association between PA and DS (Shields et al., 2010) • Low PA is an independent predictor of DS (Sund et al., 2011)

• Future research must include objective PA measures and determine causality • The importance of delivering message to adolescence regarding meeting adequate PA hour requirements is vital to both physical and mental health • All studies level 2

Dopp et al. (2012)

Quasi-experimental, Time-series design, nonrandomized Mean age = 15

• Participants significantly increased and sustained their PA, with a corresponding and sustained decrease in DS

• Repeat study with control group and increased sample size would increase power of results • Level 2

Petty et al. (2009)

RCT, no blinding Mean age = 9, range = 7–11

• Vigorous, regular PA of 40 minutes, in a directed environment decreased DS in overweight youth. Twenty minutes of similar PA may be effective in decreasing DS • Only part of the sample met criterion for adolescence

• This study needs to be repeated to extend generalizability to different age groups, BMI categories, clinically diagnosed depression, and other ethnicities • Level 1

Note. PA = physical activity, DS = depressive symptoms.

Norwegian) on four continents. The global push to understand the relationship between PA and DS in adolescents has amassed a collection of well-constructed cohort studies, one quasi-experimental trial, and one RCT. The articles’ complete findings are presented in a table format in the Supporting Information (see Table S1) with a summary table included here for perusal (see Table 1). In summarizing the articles, it is important to first understand the consistency of the findings. Four of the cohort studies employ a cross-sectional design, with impressive sample numbers. The quality of these studies (Cao et al., 2011; Hong et al., 2009; Kremer et al., 2013; Wiles et al., 2012) is evident in Worldviews on Evidence-Based Nursing, 2014; 11:6, 376–382.  C 2014 Sigma Theta Tau International

their exemplary sampling, design, and statistical analysis, with consistent results demonstrating the inverse relationship between PA and DS. Interestingly, Cao and colleagues (2011) and Kremer and colleagues (2013) find differences when comparing the additive effect of increased screen time and decreased PA on increased DS. While Cao and colleagues (2011) demonstrate an additive effect, Kremer and colleagues (2013) do not find this to be the case. This is an important aspect for future studies to address. Three of the four longitudinal cohort designs (Rothon et al., 2010; Stavrakakis et al., 2012; Sund, Larson, & Wichstrom, 2011) establish similar findings in the inverse correlation between PA and DS. The fourth longitudinal

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study by Shields, Spink, Chad, and Odnokon (2010) looks at the relationship between self-efficacy, PA, and DS. The authors find that PA and DS do not demonstrate a significant inverse correlation at midlevel self-efficacy (Shields et al., 2010). However, Shields and colleagues (2010) use a unique research design that incorporates self-efficacy, and its population is unique because their baseline levels of PA are significantly higher than other study groups. Two of the four longitudinal studies (Stavrakakis et al., 2012; Sund et al., 2011) manage a follow-up of greater than 80%, and both of these studies show a continued inverse relationship over time in some aspects of PA and DS. The quasi-experimental study (Dopp et al., 2012) demonstrates a similar level of evidence as the large cohort studies given its small size and inability to adequately power the statistical analysis. The one RCT by Petty, Davis, Tkacz, Young-Hyman, and Waller (2009) demonstrates a causal link between increased PA and decreased DS. However, this sample includes a small portion of the population within the clinical question. It is important to keep this in mind when considering the evidence from this study. This current body of evidence is also limited by its widely variable cultural input. Though it is heartening to see adolescents on four continents with a similar inverse relationship between DS and PA, it is important to note that as values change from culture to culture, so will the applicability of the tools to study such a concept.

DISCUSSION Though the findings of these studies are very consistent, one well-powered RCT and nine lower evidence papers cannot demonstrate a causal effect of increased PA on decreased DS. The original PICO question asking if PA significantly reduces DS in adolescents cannot adequately be answered with the evidence in hand. Ebell and colleagues (2004, p.555) note that a B grade is based upon “limited-quality, patient-oriented evidence.” The strength of recommendation grade for this body of evidence warrants a B grade based upon its many consistent cohort studies, one good, but underpowered quasiexperimental study and one well-constructed RCT. This body of evidence cannot establish a causal link, but does show promise as it consistently found a strong inverse correlation between PA and DS. The findings of this review reflect the outcome of the reviews of both Biddle and Asare (2011) and Dunn and Weintraub (2008), and add to the current body of knowledge regarding the relationship between PA and DS. Biddle and Asare (2011) and Dunn and Weintraub (2008) conducted a review of reviews, and utilized research that ranged from 1965 to 2006. Both papers noted that further research is necessary to extend a causal relationship to the two variables. The overall modest inverse correlational relationship found by Biddle and Asare (2011) is strengthened through this review with large, welldesigned correlational studies that demonstrate strong crosssectional and longitudinal inverse relationship between PA and DS while controlling for multiple variables.

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Previous research by Melnyk and colleagues (2006) noted that the adolescent, particularly the overweight adolescent, gets caught in a vicious cycle of unhealthy thought processes (e.g., DS) leading to unhealthy behavior choices, including lack of PA. It is important to note that some of the studies in the aforementioned body of evidence note a bidirectional relationship between the two variables. This body of evidence supports the findings by Melnyk and colleagues (2006) and encourages future study of PA and cognitive behavioral therapy interventions utilized together for the treatment and prevention of depression. After the analysis of the body of evidence for this review, Melnyk and colleagues (2013) published an RCT that reflects the link between PA, cognitive behavioral skills building, and decreased DS in adolescents. In this well-designed, blinded, cluster RCT, Melnyk and colleagues (2013) introduce a comprehensive healthy lifestyles program taught by teachers in high school health classes (i.e., Creating Opportunities for Personal Empowerment [COPE] and Healthy Lifestyles: Thinking, Emotions, Exercise, and Nutrition [TEEN]). The findings note that focusing on creating and maintaining healthy behaviors in adolescents, including activities such as daily PA, results in decreased BMI over time and improved psychosocial and academic outcomes. In addition, this RCT demonstrated a reduction in DS among initially severely depressed participants (Melnyk et al., 2013). This study lends support for further RCTs to evaluate the impact of PA on DS in adolescents, especially as a part of a comprehensive cognitive behavioral therapy strategy for depression.

IMPLICATIONS AND AREAS FOR FUTURE RESEARCH Given that the current body of evidence indicates the need for further RCTs to establish a causal link between increased PA and decreased DS, encouraging future research to establish causal direction through rigorous RCTs is important for the healthcare field. PA as a potential adjunct treatment for depression maintains its allure because of the perceived ease and minimal cost with which it can be implemented among adolescents. It also is important to note that PA as a treatment for depression may augment evidence-based cognitive behavioral therapy, the gold standard treatment for depression. Research that studies these two modalities together may also support PA as a helpful adjunctive therapy. Whitehead (2006) found that nursing maintains a responsibility to provide health education to patients and their families. This begins with careful screening for DS in adolescents to determine who is most at-risk. Though this review finds no definitive evidence of a causal relationship between PA and DS, healthcare providers can and must deliver health education to adolescents and their parents or caregivers regarding the relationship between PA and DS and the importance of initiation and maintenance of the recommended 60 minutes of PA per day (CDC, 2013). Though Ham and Allen (2012) describe Worldviews on Evidence-Based Nursing, 2014; 11:6, 376–382.  C 2014 Sigma Theta Tau International

Evidence Review the difficulties perceived by healthcare providers in working with this population, it is imperative to take the time to educate families regarding healthy behaviors. Whitehead (2006) further delineates the importance of broader health promotion activities by healthcare providers that are crucial to societal wellness. Whitehead (2006) describes the need for nursing to engage community institutions that drive health policy as a way to engage health promotion. This review provides support for broad healthcare policies that sustain youth in their attempts to attain the recommended PA levels through the education system or safe passage laws that create the environment in which to increase PA. A summary of recommendations that healthcare providers might consider based upon the described evidence are listed in Linking Evidence to Action.

CONCLUSIONS The original intention of this paper was to perform a systematic review of the research that has evaluated the impact of PA on DS in adolescents, and to determine if the strength of the evidence might support PA as a complementary approach to combat DS in adolescents. This review finds evidence for a moderate recommendation (i.e., B grade), based on the SORT tool algorithm (Ebell et al., 2004), with nine level-of-evidence 2 primary research articles, and only one level-of-evidence 1 primary research article. Causality cannot be established based upon this body of research. Therefore, rigorous randomized controlled trials need to be conducted to definitively establish PA as a treatment approach for DS. The importance of preventing and treating DS in this population cannot be overstated. With depression as the worldwide leading cause of disability (WHO, 2012), it is vitally important to continue to investigate novel ways to combat this disease process. At this point in time, healthcare providers can educate parents and their adolescents about the inverse relationship between PA and DS as a form of primary and secondary prevention. In addition, healthcare providers can utilize this knowledge to promote policies that create an environment that supports safe and effective PA. Open communication, health education, and health promotion with parents, adolescents, and communities that involves knowledge-building surrounding the recommended PA guidelines of at least 60 minutes per day (CDC, 2013) is a crucial start to protecting adolescents and encouraging the conversation regarding the strong inverse relationship between these two variables. WVN

LINKING EVIDENCE TO ACTION Tips for Healthcare Providers Based on Best Evidence

r Screen adolescents for depression. r Talk to parents and their adolescents about the strong inverse correlation between DS and PA.

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r Teach families about the recommendation for 60 minutes of daily PA in youth.

r Engage in research to determine if there is a causal link between PA and DS.

r Promote public health policy that recognizes the importance of PA for adolescents.

Author information Patricia Bursnall, graduate student, Department of Nursing, Georgetown University School of Nursing and Health Studies, Colorado Springs, CO, USA Address correspondence to Patricia Bursnall, Georgetown University School of Nursing and Health Studies, 1608 W. Cheyenne Road, Colorado Springs, CO, 80906; [email protected] Accepted 23 May 2014 C 2014, Sigma Theta Tau International Copyright 

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SUPPORTING INFORMATION Additional supporting information may be found in the online version of this article at the publisher’s web site: Table S1. Full Summary of Evidence

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