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SYNOPSIS: The authors of this review article found a suggestive link between stopping exercise and the onset of depressive symptoms in healthy adults, especially in women.
SOURCE: Morgan JA, Olagunju AT, Corrigan F, Baune BT. Does ceasing exercise induce depressive symptoms? A systematic review of experimental trials including immunological and neurogenic markers. J Affect Disord 2018;234:180-192.
Exercise helps prevent depressive disorder and can be instrumental in management of depressive symptoms.1,2 Any lingering skepticism regarding this relationship was laid to rest earlier this year with the publication of the results of the HUNT Cohort study. The authors of this well-regarded, prospective Norwegian investigation followed more than 33,000 healthy adults for 11 years and concluded that even low levels of activity protect against the onset of depressive symptoms in a non-depressed population.2
To further understand the complex relationship between exercise and depressive symptoms, Morgan et al chose to study this relationship from a different perspective; if exercise helps prevent depressive symptoms, is cessation of exercise linked to the emergence of depressive symptoms? In a comprehensive search for published studies looking at cessation of exercise and emergent symptoms of depression, Morgan et al were unable to locate any studies looking at this phenomenon in a depressed population. After screening nearly 1,000 studies, the authors found six relevant studies3-8 looking at the relationship between brief cessation of exercise and the emergence of depressive symptoms in a non-depressed, healthy, regularly active adult population. None of the studies looked at the emergence of full-blown depressive disorder or any specific psychiatric disorder; all looked at emergent symptoms or mood states, such as fatigue, decreased concentration, and lack of energy.
The six studies included 152 adults. In at least one study, there appeared to be a gender-based response, with women appearing more prone to develop depressive symptoms after stopping exercise. As only about one-third of the total participants from the studies were women, Morgan et al believed this uneven gender balance may have skewed results and that more robust development of depressive symptoms may be seen with a more balanced gender pool.
In all selected studies, the primary outcome — onset and intensity of depressive symptoms — was measured with specified screening tools (generally structured screens) according to each study protocol. Although several different tools and screens measuring depressive symptoms were used, the profile of mood states (POMS) was used most consistently across the group.9
The POMS is a scale-based rating tool used to assess current mood. Participants are asked to rate themselves on a scale of 1 to 4 on a variety of categories regarding how they feel at the time of assessment. These categories range from sad, angry, and tense to confident and energized. A total score is calculated by combining the “negative” subscores and subtracting the more positive subscores.9,10 Thus, in general, a higher POMS score indicates a higher self-rating of more depressive symptoms.
There was heterogeneity not only in tools but also in timing of measurement. Emergence of depressive symptoms was examined at three days in one study, one week in two studies, and three weeks in four studies. The range of depressive symptoms was wide and included anxiety, dejection, anger, fatigue, and confusion.
Three studies measured and reported changes in inflammatory markers associated with depression. Aerobic exercise (a range of types and intensity) was the only form of exercise evaluated across all six studies. None of the studies reported any adverse events other than the development of depressive symptoms. None of the observational studies considered the reasons for stopping exercise as a confounding factor.
Two of the studies were randomized, controlled trials (RCTs) and were of higher quality than the four non-RCTs. Only three of the studies (including the two RCTs) had designated control groups for comparison. In each case, the control group continued exercise as usual. None of the studies attempted to compare or examine mood states post-cessation of exercise to mood states in a never-exercising population.
Morgan et al noted the quality of the six studies varied from moderate to good for the two RCTs and very poor to moderate for the non-RCTs. In the final analysis, Morgan et al assigned extra weight via statistical analyses to higher-quality investigations. However, given that the RCTs included only 66 participants in total, it is difficult to draw firm conclusions from the results. Notably, the risk of bias was believed to be unclear in most studies.
Given the clear weaknesses of the studies, Morgan et al noted “serious concerns about inadequate methodologies including lack of controlling for confounding factors … our findings must be considered with caution.” However, they also cited valid and compelling reasons to review these studies and a direction for future investigation. See Tables 1, 2, and 3 for results.
National and international public health guidelines for physical activity are clear that regular physical activity is crucial in prevention and treatment of depressive symptoms.11,12 According to the World Health Organization (WHO), these guidelines are meant to “improve cardiorespiratory and muscular fitness, bone health, reduce the risk of NCDs and depression.”13 WHO physical activity recommendations state:13
The importance of exercise to public health and depression is not in question. However, the related question posed by Morgan et al — do depressive symptoms emerge after cessation of exercise? — not only is relevant to public health but also is highly significant to everyday clinical practice. Notably, this question does not refer to emergence of depressive disorder per se, but more narrowly looks at symptoms such as fatigue, lack of energy, and decreased motivation related to exercise cessation. Whether these symptoms could lead to development of a depressive disorder is beyond the scope of this investigation and remains an open question. Looking for evidence of a relationship between exercise cessation and depressive symptoms is just one step toward addressing this and other broader questions regarding a relationship between exercise and mood states.
As noted, Morgan et al found that few quality studies exist and that the numbers involved are too low to draw firm conclusions. The heterogeneity of scales used to measure depressive symptoms make the studies difficult to compare and difficult to consolidate to perform a meta-analysis.
Furthermore, none of the studies used a functional screen or structured interview to measure depressive symptoms and instead relied on more subjective measures of internal state. POMS essentially is a self-rating instrument for different mood states across a spectrum. It is well-regarded as a tool to evaluate acute mood changes in a healthy population. However, this scale does not allow assessment of any functional effect from the mood changes and is most valid when large number of subjects respond.9
The highest quality studies were the two RCTs. Unfortunately, neither used a mechanism to blind the control group; the self-rating nature of the scales measuring the effect of stopping exercise makes it difficult to remove bias and suggests the usefulness of outside objective measurement for future studies.
Morgan et al noted that the relatively low number of women across the studies may have skewed the results, given the consolidated group of women showed a higher mean number of depressive symptoms than the men after cessation of exercise. This may be significant, and future studies should look at gender-specific responses, but the general low quality of the studies makes even suggestive conclusions difficult.
The results of no change to negative changes in inflammatory markers after cessation of exercise are objective and measurable, and are unexpected given our knowledge of reduced inflammatory markers with exercise and increased markers in depression. This is an additional area for high-quality, high-participant studies. Although many of these factors affecting study quality detract from regarding this review seriously, the study still is relevant and certainly gives evidence to the need for future high-quality studies.
Perhaps of most value to clinical practice from this review is the reminder to incorporate questions about exercise and changes in exercise frequency into a clinical history. Tell patients that preliminary studies show symptoms consistent with an early depressed state may emerge when stopping exercise, even in healthy, non-depressed individuals. It is important to note that there is no evidence from this review regarding severity of depressive symptoms or interference with everyday functioning and no evidence of emergence of a full-blown depressive disorder. The most likely practical remedy for emergence of these symptoms is to resume the exercise, but this may not always be possible (such as after an injury.) It is helpful to remind patients that results from the large-scale HUNT Cohort Norwegian study indicate that even low levels of physical activity can prevent the emergence of depressive symptoms.2
Discussing the results of this comprehensive review study can springboard a discussion and provide a valuable reminder of the important role of physical activity in mental health and control of depressive symptoms. Likewise, discussing such issues can remind us all of the value of self-examination and awareness of mood states — an invaluable tool in managing powerful emotions in daily life.
Financial Disclosure: Integrative Medicine Alert’s Executive Editor David Kiefer, MD; Peer Reviewer Suhani Bora, MD; AHC Media Executive Editor Leslie Coplin; Editor Jonathan Springston; and Editorial Group Manager Terrey L. Hatcher report no financial relationships relevant to this field of study.