Mood disorders: Does exercise matter?
By Kendall Wisehart DPT, ATC
In physical therapy, it’s easy to get caught up in the physicality of it all – muscles, bones, joints, biomechanics, and our favorite, physics. Unfortunately, what doesn’t get this well-deserved attention are the non-physical benefits, the mental and emotional benefits. Specifically, when examining mood disorders such as depression and bipolar disorder studies found that exercise impacts both physical and mental health outcomes. Exercise also positively affects conditions frequently associated with mood disorders such as anxiety, pain, and insomnia or other sleep disturbances.
Several mechanisms have been proposed for the anti-depressive effects of exercise, which can be divided into two categories – psychological and biological. Psychological variables include increased feelings of control (autonomy), physical wellness, quality of life, improved self-esteem / mood. Biological variables include several growth factors, oxidative stress, and genetics and their role in exercise-induced neurogenesis and anti-depressive effects.
“Studies have shown that after several weeks of moderate intensity exercise, oxidative stress and pro-inflammatory markers are decreased.”
Most of the recent work related to the anti-depressive effect of exercise and biological makers has focused on the role of BDNF or Brain Derived Neurotrophic Factor. By definition, BDNF supports neurogenesis or the growth of neurons. In fact, antidepressant medications up-regulate BDNF and patients with mood disorders exhibit lower levels of BDNF compared to their healthy counterparts. Simply put, BDNF may be the primary mechanism of the anti-depressive effects of exercise. While BDNF is important enough to have it’s own dedicated blog post, what’s important to know is that BDNF is essential in nerve survival, growth, and pathological levels of BDNF may contribute to psychological disorders and chronic pain sensitization.
Exercise may also impact oxidative stress. We’ve all heard the term anti-oxidant and generally accepted it as a good thing. Without going into the specifics of cellular (mitochondrial) energy production, it’s important to understand that oxidation is a normal part of the energy production system of the cell. In the absence of anti-oxidant defense, oxidative stress and cellular damage can occur. Fortunately, exercise can impact oxidative stress. This is especially important for those with mood disorders in which there are increases in inflammation and oxidative stress. Studies have shown that after several weeks of moderate intensity exercise, oxidative stress and pro-inflammatory markers are decreased. On the flip side, high intensity exercise increased oxidative stress. The summary here is simple, a balance of exercise intensity is key when achieving both physical and psychological benefits of exercise.
Finally, based on recent research, exercise has been associated with epigenetic changes that are beneficial for those with mood disorders. Epigenetic changes refer to changes in gene expression without an actual change in DNA sequence. For example, BDNF can be upregulated through these types of exercise induced changes. It has also been suggested that exercise promotes epigenetic changes that promote homeostasis, neuroplasticity, circadian rhythms, and endocrine and immune regulations.
Others have suggested that exercise induced epigenetic changes can reduce the aging process and have beneficial effects on the musculoskeletal system across the lifespan.
Exercise may be an acceptable alternative or adjunctive therapy to enhance mood, functioning, and co-morbid conditions for individuals with mood disorders. Overall, there is promising evidence to support the use of exercise in the treatment of mood disorders. Future research will focus on specific frequencies, durations and types of exercise for specific mood disorders.
For now, balance is key and something is always better than nothing – even a short walk can have it’s benefits (see upcoming post).