Exercise May Improve Cognitive Function in Depression
Tracy L. Greer of the University of Texas Southwestern in Dallas presented an abstract at the 51st Annual Meeting of the National Institute of Mental Health’s New Clinical Drug Evaluation Unit (NCDEU) in 2011 that suggested that exercise improved the cognitive function of patients being treated with selective serotonin reuptake inhibitors (SSRIs) for major depressive disorder.
Thirty-nine participants reported cognitive impairment at baseline. Subjects were randomized to receive antidepressant treatment in the form of an SSRI augmented by either an exercise regimen designed to burn 16 kilocalorie/kg per week (kkw) or one designed to burn 4 kkw. Both exercise regimens resulted in improved response time on a measure of attention, and for the higher intensity (16 kkw) exercise group, there were improvements in response time for visual memory tasks as well as decreased errors on an executive function task.
Editor’s note: There is a somewhat mixed literature on the efficacy of exercise in potentiating antidepressant effects of other treatments. Recent data by Fred Gage and colleagues showed that in animals, exercise increased not only brain-derived neurotrophic factor (BDNF), which seems to be necessary for long-term learning and memory, but also the formation of new neurons (neurogenesis). Gage found that new neurons that migrated to the dentate gyrus of the hippocampus were more excitable than older neurons and were important in a variety of cognitive tasks.
The newer neurons could more precisely distinguish between different stimuli, while the older neurons were sufficient only for discriminating stimuli that were widely and obviously different from each other.
Thus, the increase in new neurons and BDNF that may follow exercise and antidepressant use may be associated with some cognitive improvement in depression, particularly in the realm of response speed and perhaps also in making relatively fine discriminations among relatively similar objects.
While not much evidence for the effect of exercise on cognition has been collected in humans, exercise has many other benefits. Since it is good for cardiovascular fitness and wellbeing, as well as potentially generating new neurons that could play an important role in fine cognitive discriminations, encouraging exercise in depressed patients (especially as their depression improves and they have renewed motivation to engage in exercise regimens) could be of value, even if exercise is not a guaranteed enhancer of antidepressant effects per se.
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