By Ellen Feldman, MD

Altru Health System, Grand Forks, ND

Dr. Feldman reports no financial relationships relevant to this field of study.

SYNOPSIS: Physical exercise may alleviate symptoms of depression in adolescents.

SOURCE: Carter T, Morres ID, Meade P, Callaghn P. The effect of exercise on depressive symptoms in adolescents: A systematic review and meta-analysis. J Am Acad Child Adolesc Psychiatry 2016;55:580-590.

SUMMARY POINTS

  • This is a comprehensive review and meta-analysis of randomized, clinical trials conducted between 1982 and 2015 regarding the effect of exercise on depression in teens.
  • When looking at all eligible studies, exercise shows a moderate effect on decreasing depressive symptoms in adolescents.
  • When narrowing the analysis to studies with participants diagnosed with depression (vs. a non-diagnosed, community-based population), the effect of exercise looks more substantial.

Untreated depression in teens can affect quality of life for years. The developmental tasks of adolescence include the ability to make and sustain social relationships, develop a capacity for delayed gratification, and navigate the complex task of separation from parents; these all may be slowed or skewed by the weight of depressive symptoms.1 Treatment of this highly prevalent disorder (approaching 20% of teens ages 13-20) is essential and typically involves a multimodal approach of medication, adjunct therapies, and lifestyle interventions.2

Carter et al investigated the effect of exercise in treating depressive symptoms in teens by conducting a meta-analysis. To identify appropriate, well- designed, and relevant studies, they applied specific criteria including:

  1. The study was conducted as a randomized, controlled trial investigating depression in teens between 13-17 years of age.
  2. The study incorporated physical activity as an intervention.
  3. The publication was in English between the years of 1982 and 2015.
  4. The study included baseline, control, and outcome results measuring depression.

Characteristics of the Studies included in the Meta-analysis

Eleven studies meeting all inclusion criteria were identified; out of these studies, eight had sufficient data to analyze and calculate effect size. A total of 384 individuals (from the eight studies) were involved in the meta-analysis; median sample size was 60; most were mixed sex; the mean age of the teens in each trial was between 14.7-17 years of age. Recruitment strategies for the studies varied from obtaining volunteers from a general high school population to more rigid inclusion of teens in a clinic population diagnosed with depression to teens diagnosed with depression on inpatient units. Thus, the severity of depressive symptoms at entrance to the studies varied widely.

Although all trials measured depression using self-report standardized scales, there was no consistent scale or measure used. The Children’s Depression Inventory3 was used in two of the eight studies; several other scales were employed in the other studies, including the Beck Depression Inventory (measuring depression and anxiety)3 and the Beck Depression Scale.4

All trials included exercise at least three times weekly for 6-40 weeks, with a median duration of 11 weeks. The intensity of activity ranged from light to moderate, without any standard type or category of activity. Few trials looked at baseline level of exercise or activity or adjunct exercise (apart from the intervention during the study period).

With recruitment, intervention techniques, and measurement tools differing trial to trial, the authors looked at several measures to determine the effect of exercise within the pooled samples. Among several other statistics, standardized mean difference (SMD) and level of heterogeneity were reported. The level of heterogeneity was thought to be particularly important to determine if comparable studies were being analyzed.

Results

Table 1 represents analyzed results pooled and weighted from the eight studies. Table 2 shrinks the pool to the five studies that included only clinically depressed populations of teens. A lower depression score is indicative of less severity of depressive symptoms. Both study groups appear to show a moderate and statistically significant treatment effect from exercise on depressive symptoms. The lower heterogeneity (under 50%) for the clinical population lends more credibility to the concept that the studies are measuring the same intervention effect.

Table 1: Pooled Results for the Eight Studies Included in this Meta-analysis

 

Number of participants

SMD (standardized mean difference)

P value

Heterogeneity (I2)

Experimental

220

-0.48

0.01

67%

Control

164

     

Table 2: Clinical Sample and Pooled Results for the 5 Studies that Included Only Clinically Diagnosed, Depressed Study Participants

 

Number of participants

SMD (standardized mean difference)

P value

Heterogeneity (I2)

Experimental

99

-0.43

0.04

44%

Control

84

     

COMMENTARY

Adolescence is a period of change The negative implications of untreated depression during this time period can reach into the future; the effect of successfully treated depression in teens potentially is far-reaching. Adolescents with untreated depression are at higher risk for substance abuse, other psychiatric comorbidities, and suicide.1,2,5 Most mental health professionals and medical providers agree that treatment of depression during adolescence is important, but a major dilemma and disagreement in treating this disorder lies in the specific modality selected for intervention. The question is not should we treat, but how should we treat?

Many providers look to medication as a first step in treatment for adolescent depression. In the late summer of 2016, just after the publication of this meta-analysis looking at exercise and teen depression, another meta-analysis regarding treatment of depression in children and adolescents was published.6 This second meta-analysis focused on treatment with antidepressant medication. From a pool of 34 trials and more than 5,000 participants, the researchers found that only fluoxetine was statistically more significant in terms of efficacy than placebo. In fact, the paper concluded:

“… considering the risk-benefit profile of antidepressants in the acute treatment of major depressive disorder, these drugs do not seem to offer a clear advantage for children and adolescents. Fluoxetine is probably the best option to consider when a pharmacological treatment is indicated.”6

These two meta-analytic studies, while overlapping in some areas, cannot be compared head-to-head given significant differences, including age range of the participants, number of participants, and quality of the studies. However, it is worth reflecting that the relatively moderate effect of exercise on depressive symptoms rises in significance when viewed in the context of the results of the antidepressant studies.

As mentioned earlier, the standard of care in treatment of adolescent depression is multimodal.3 Known side effects (including the “black box” warning regarding emergence of suicidal thoughts) and questions about the long-term effect of antidepressant medications on the developing brain concerns many parents, guardians, teens, and providers alike.3,6 Non-pharmacologic therapies, including cognitive behavioral therapy, a specific type of talk therapy, have solid studies supporting efficacy, but geographical and financial barriers to well-trained therapists can make this treatment difficult to access.7 Part of the excitement about exercise as an intervention is that it has few of these barriers and limited negative side effects.

However, one potential negative side effect is the concern that a teen may perceive that exercise alone should “fix” depression. It is quite important for providers to help patients and families understand these studies, the serious nature of untreated or undertreated depression, and various options for treatment. It also should be noted that positive side effects of exercise as a treatment for depression are numerous and include the full benefits of exercise on health in general.

This group of researchers set out to investigate the role of exercise in treatment of depressive symptoms in adolescence through a comprehensive meta-analysis. A survey of studies over a period of more than 30 years yielded only 11 adequate studies, and just eight of these had enough information to include in the meta-analysis. These numbers alone point to the need for better and more comprehensive, well-designed studies in this area.

Working with the information and data we have, it does appear that the results of this meta-analysis support exercise as an intervention to alleviate, at least partially, depressive symptoms, especially in adolescents with a diagnosis of depression. The evidence is not conclusive, but certainly is suggestive. The degree to which symptoms are improved seems significant — even more so when we look at evidence for the efficacy of pharmacological treatments (as noted above).

Interestingly, the studies in the meta-analysis looked at symptom alleviation and not disease or disorder remission; there is no evidence from these studies regarding exercise as a standalone treatment in depression or in achieving full resolution of a depressive episode. Likewise, there is no evidence from these studies regarding using exercise as preventive intervention.

Unfortunately, the studies gave no concrete information regarding the presence or absence of any concurrent treatment for depression (pharmacological or other), leaving a clear knowledge gap regarding the role of exercise as an adjuvant treatment. Certainly, this is an area ripe for future investigation.

The impact and importance of a meta-analysis to understand the medical significance of an intervention grows in significance when few studies are available for analysis and when divergent methods and measurements exist. In this case, the results of the pooled analysis allow a provider more confidence in advising depressed teen patients to add exercise to a treatment regimen.

It is hopeful that another outcome of this meta-analysis will be that future researchers will pursue careful, well-designed studies to identify and categorize more precisely the role of exercise in treatment of depression. Knowing specifics about the type of activity needed (such as level of intensity needed, time-dependent criteria, group vs. individual activity) and gaining a more complete understanding of the mechanism of action during developmental stages will be helpful in clinical applications of this intervention.

For now, a provider is on solid ground letting depressed teens and guardians know it is likely that exercise plays a role in alleviation of depression symptoms. As symptom relief is achieved, the morbidity and mortality associated with teen depression is likely to remit as well. It appears that the risks associated with recommending exercise are slim and the potential gains great. Still, it remains prudent to caution patients that our knowledge about the role of exercise in depression is at an early stage and that effective treatment of depression usually involves multiple complementary interventions. Although exercise alone may not be the complete answer to teen depression, the evidence presented in this study suggests exercise can and should play a prominent role in treatment of this complex disorder.

REFERENCES

  1. National Institute of Mental Health. Major Depression Among Adolescents. Available at: https://www.nimh.nih.gov/health/statistics/prevalence/major-depression-among-adolescents.shtml. Accessed Nov. 12, 2016.
  2. ChildStats.gov. Adolescent Depression. Available at: http://www.childstats.gov/americaschildren/health2.asp. Accessed Nov. 12, 2016.
  3. Stockings E, Degenhardt L, Lee YY, et al. Symptom screening scales for detecting major depressive disorder in children and adolescents: A systematic review and meta-analysis of reliability, validity and diagnostic utility. J Affect Disord 2015;174:447-463.
  4. American Psychological Association. Beck Depression Inventory (BDI). Available at: http://www.apa.org/pi/about/publications/caregivers/practice-settings/assessment/tools/beck-depression.aspx. Accessed Nov. 22, 2016.
  5. Thapar A, Collishaw S, Pine DS, Thapar AK. Depression in adolescence. Lancet 2012;379:1056-1067.
  6. Cipriani A, Zhou X, Del Giovane C, et al. Comparative efficacy and tolerability of antidepressants for major depressive disorder in children and adolescents: A network meta-analysis. Lancet 2016;388:881-890.
  7. Clarke G, DeBar LL, Pearson JA, et al. Cognitive behavioral therapy in primary care for youth declining antidepressants: A randomized trial. Pediatrics 2016;137:e20151851.