From American Journal of Lifestyle Medicine
Exercise in the Prevention and Treatment of Adolescent Depression: A Promising but Little Researched Intervention
Abstract:
Despite a dramatic increase in the number of treatment studies for adolescent major depressive disorder in the past 15 years, the majority being clinical trials of medications and cognitive behavioral therapy, response rates have been modest and remission rates low. Moreover, most positive responders posttreatment have many residual symptoms, significant functional impairment, and high rates of relapse. There is a need for the development of new, more effective interventions to treat this severe, chronic condition that usually persists into adulthood with poor long-term outcomes. Findings from preliminary treatment studies suggest that exercise may have the potential to be efficacious as a monotherapy or as part of a combined treatment for adolescent major depressive disorder. This review summarizes the findings and analyzes the design flaws of randomized trials of exercise to treat adolescent depression, offering recommendations on how to design more methodologically sound studies with an emphasis on subject selection criteria; issues related to control conditions, types of diagnostic interviews, and measures needed to establish the diagnosis of depression; types of exercise treatments; and appropriate outcome measures. Future studies of exercise to treat and prevent adolescent major depressive disorder need to be comparable to state-of-the-art treatment studies of pharmacotherapy and cognitive behavioral therapy in this population to more accurately determine its efficacy and potential public health benefits.
Introduction
Adolescent depression is a major public health problem in the United States and throughout the world.[1-11] Major depressive disorder (MDD) in teens is common with point prevalence rates of 3% to 9%.[12-15] In the United States, it is estimated that by the time adolescents reach adulthood, 25% of them will have experienced at least one episode of MDD.[2] Recent studies show a secular increase in its prevalence,[16] and many serious youth problems such as suicide,[17,18] substance abuse,[19] cigarette smoking,[20] teen pregnancy,[21] impaired psychosocial functioning,[22] and school failure[23] have been linked to untreated depression. Moreover, adolescent depression has been shown to be a chronic condition persisting into adulthood with multiple recurrences and significant morbidity.[24,25] Therefore, successful treatment of teen depression is important not only in reducing the suffering, morbidity, and mortality from the disorder but also in preventing the development of other adverse long-term psychosocial and health outcomes.
Most of the research on this illness has been for adolescent MDD, but even subsyndromal depression is linked to significant functional impairment and an increased risk of developing MDD. For example, in a prospective study of more than 2000 adolescents,[22] teens with subthreshold depressive symptoms showed significantly greater functional impairment compared with teens diagnosed with conduct disorder. Thus, adolescents with subclinical symptoms of depression represent an equally important intervention target to prevent worsening of symptoms and to improve functional outcomes.[26-28]
Although there has been a dramatic increase in the number of treatment studies of adolescent MDD in the past 10 to 15 years, most clinical trials have tested the efficacy of medications, primarily the selective serotonin reuptake inhibitors (SSRIs), and cognitive behavioral therapy (CBT).[29-34] Medications and CBT have achieved low rates of remission, and positive responders have a high rate of relapse with residual symptoms being associated with an increased risk of recurrence.[35-37] Most studies of adolescent depression define a positive response as (1) a 30% to 50% improvement in symptoms on a standardized rating scale or (2) a global rating that the individual is much or very much improved. Even with these criteria for positive response, which do not require remission of the illness, it is estimated that only about 60% of study participants respond to treatment, and most still have significant symptoms and functional impairment at study's end.[36,38] Remission, the ultimate goal of treatment, is even lower, ranging from 30% to 40% in most medication treatment studies.[36] Moreover, the Food and Drug Administration's (FDA's) controversial 2004 issuance of a black box warning that antidepressants are associated with an increased risk of suicidal ideation in depressed youth was followed by a dramatic reduction in prescribing these medications and the first increase in the teen suicide rate in a decade.[39,40] Although many subsequent studies have not shown this increased risk of suicidal ideation, the fear engendered in families and practitioners by the black box warning has made these medications a less acceptable treatment alternative, creating a potential public health crisis with respect to youth suicide risk and, therefore, an urgent need to develop effective new treatments for adolescent MDD.
The mixed findings in clinical trials of the current major treatment modalities of adolescent MDD, showing modest efficacy of medication and CBT, in conjunction with fears among practitioners and the general public about the potential dangers of medication, point to the need to develop new interventions with greater efficacy, safety, and acceptability to patients, families, and physicians.[41] As has been the case with the development of most other treatments of pediatric psychiatric disorders that are also common in adulthood, it is necessary to extrapolate from adult studies of exercise treatment of depression when justifying the need for research of physical activity in adolescent populations because virtually all well-designed studies have been done with adults. First, there is evidence that physical activity and, more specifically, structured exercise could potentially play an important role in the treatment of adolescent depression because it may be more acceptable to the general population than SSRIs or CBT. A recent survey of 2692 adult patients who had been treated for depression in Australia provides some hint about the possible acceptability of this treatment modality for teens even though the study was conducted in adults.[42] Patients were asked to check which treatments they had tried and rank which seemed most effective. The survey found that 2141 had tried exercise compared with 672 who had tried venlafaxine and 1221 who had tried CBT. Using a scale of 0 to 3 with 3 being most effective, the effectiveness score for exercise was 1.70, second only to venlafaxine with an effectiveness score of 1.73, the highest effectiveness score of all the treatments surveyed. The second most widely used treatment, CBT, had an effectiveness score of 1.63. These data suggest that exercise may be more acceptable to patients as a treatment for depression because it was the most commonly used intervention by respondents and perceived by them as one of the most effective. Possible explanations for these findings are that exercise is a normal activity that is not associated with the stigma of other types of treatment, is inexpensive, and is regarded by most of the population as an important way to promote and maintain good health. Moreover, exercise treatment studies of adult MDD, including those in which exercise was a monotherapy,[43-47] a combination therapy,[48-50] and an augmentation therapy with antidepressant medication,[51] have had remission and response rates comparable to those of medication and psychotherapy, supporting the rationale for conducting similar treatment studies in depressed youth.[44-46,49-54]
In adolescents, data are sparse regarding the efficacy of exercise in the prevention and treatment of depression. A 2006 Cochrane Review of exercise for the prevention and treatment of adolescent depression found a small effect in support of exercise,[55] but that conclusion was based on very few randomized clinical trials that the reviewers felt were of low methodological quality. The authors concluded that, based on the current published research, it is unknown whether exercise is an efficacious treatment for adolescent depression due to a very small number of studies, extremely heterogeneous subject samples with respect to diagnosis and symptom severity, and diagnostic and outcome measures that make it difficult to interpret study findings.
We believe that the evidence base for the efficacy of exercise in adult MDD is sufficiently robust to justify studies of physical activity and exercise for the prevention and treatment of adolescent depression. The primary aim of this article is to provide an overview of what we believe are improvements needed for randomized clinical trials to more accurately assess the efficacy and benefits of exercise in adolescent depression and in preventing the development of depression in this age group. Because the Cochrane Review[55] is comprehensive and recently published, we will use it as our major source for reviewing the current state of the field that is based on unique issues related to the treatment of MDD and exercise. We first summarize the findings and design flaws of existing, published studies. Then we discuss the unique issues that are critical to address to design methodologically sound exercise treatment studies of depression in adolescents, a developmental stage that requires modification of study designs employed in adults. We emphasize, in this review, issues pertaining to subject selection criteria, types of diagnostic interviews and measures needed to establish the diagnosis of depression and excluded disorders, special issues related to control groups, types of exercise treatments that should be investigated, and appropriate outcome measures. In this section, we provide a conceptual model that we hope will be useful for guiding researchers who wish to pursue studies of exercise effects on adolescent depression. Finally, we make specific recommendations that we believe can improve the internal validity of future efficacy trials and the generalizability of new effectiveness studies that have the potential to be widely disseminated and reduce the high level of morbidity, mortality, and suffering caused by this disorder.
For further information: http://www.medscape.com/viewarticle/583549?src=mp&spon=8&uac=45143PK
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