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Comorbidity of depression and anxiety in exercise research
Overwhelming evidence supports the efficacy of exercise in the treatment of depression and anxiety. Actually, that is a fallacy. There is evidence on exercise as a treatment for depressive or anxiety disorders,1,2 but these disorders co-present more than they occur in isolation,3 and we know very little about the effects of exercise on comorbid depression and anxiety disorders. To improve the clinical translation of research, the reality of comorbid depression and anxiety needs to be moved from a sentence in the limitations section of exercise trials to the title of a new line of study. Trials screen out people with comorbid depression and anxiety disorders or do not consider the potential confounding effects of comorbidity on study outcomes. Although this allows for controlled testing of efficacy, it comes at the cost of ecological validity. The comorbidity of depression and anxiety is underrepresented in estimates of disease burden and mental disorder cost. It is time to ensure patients with depressive and anxiety disorders receive evidence-based exercise prescription. This will not require innovative methodologies—it simply requires a practical perspective in trial design (eg, more inclusive selection criteria, diagnosis and monitoring of depression and anxiety). Only by addressing the reality that is comorbid depression and anxiety can we close the gap between mental health exercise research and translation.4 This correspondence is a call to arms for mental health-care professionals and exercise and mental healthcare researchers to acknowledge the reality of comorbid depression and anxiety disorders. Specifically, we highlight the need to diagnose, research, report, and treat this commonly overlooked scenario. Diagnose it: diagnostic testing of depression and anxiety comorbidity is an instrumental first step in comprehensive treatment. Research it: include potential participants with comorbid depression and anxiety in trials to understand the effects of exercise treatment on depression and anxiety symptoms within this common population. Report it: researchers must describe the co-presentation of depression and anxiety in study populations and test whether this moderates treatment effects. Treat it: rather than depression and anxiety symptoms being treated as two isolated disorders, their comorbidity should be acknowledged and accounted for by mental health-care professionals as well as exercise interventionists.