A new study shows that increased physical activity restores brain neuroplasticity in depressed individuals.
The benefits of exercise for the treatment of depression have been demonstrated numerous times over the years. The mechanisms behind this effect have, however, remained mysterious. A new study published in Frontiers of Psychiatry sheds some new light on this mystery. It showed that exercise increased neuroplasticity in depressed subjects.
Neuroplasticity can be thought of as the brain’s ability to remodel itself in response to environmental changes. It is a complex phenomenon, controlled mainly by genes that code for a bevy of small protein molecules with names like “brain-derived neurotrophic factor” (BDNF). Sensory inputs trigger this remodeling. It consists of alterations in the connections between neurons, some links becoming stronger and others weaker as new circuitry is laid down and communication pathways between brain areas change. Antidepressant medications are believed to help depression by enhancing neuroplasticity and the new brain-stimulation treatments for depression like repetitive transcranial stimulation (rTMS), appear to do the same by directly stimulating the cortex with tiny electrical impulses.
The study was carried out on 41 subjects who had been hospitalized for depression. After they had recovered enough from their symptoms to participate in the research, they were divided into two groups. For a total of three weeks, one group participated in exercise groups three days a week while the control group played (sedentary) games requiring them to use logic and deduction to solve puzzles, also three days a week.
Before and after the three-weeks of their respective interventions, each subject’s level of neuroplasticity was estimated using a model of “brain training” called paired-association stimulation (PAS) protocol. PAS consists of electrically stimulating the nerve at the base of the thumb while simultaneously using an rTMS device to deliver magnetic impulses to the area of the motor cortex that controls the thumb muscles, resulting in a brief flexing of the thumb muscles. This dual stimulation “trains” the underlying motor cortex in about 30 minutes. It makes it more sensitive to the magnetic impulses, which can cause thumb movements at lower and lower intensities. The robustness of the response to the PAS “training” (“PASeffect”) is thought to be a measure of neuroplasticity.
Before and after their programs, the subjects’ level of depression was assessed using the self-rated Beck Depression Inventory-II and the clinician-administered Hamilton Depression Rating Scale. In both groups, there was a direct correlation between the PASeffect and the degree of depression at baseline. Subjects with a higher depression score had a lower PASeffect, i.e., the brain showed lower neuroplasticity.
At the end of the study, the group that exercised had significantly lower depression scores than the group that participated in sedentary activities. Also, their PASeffect scores were higher, showing that their neuroplasticity had improved. Again, there was a direct correlation between depression level and PASeffect. The subjects whose depression had improved the most showed the greatest improvement in neuroplasticity as measured by the PASeffect.
PAS-induced plasticity is known to be higher in physically active healthy subjects compared to those with a sedentary lifestyle and the authors suggest that exercise, which has been shown to increase metabolism and oxygenation, modulate neurotransmitters and enhance the release of neurotropic proteins like BDNF in the brain are some of the mechanisms by which exercise enhances neuroplasticity. They suggest that exercise programs be incorporated into the treatment of depression.
The conclusion: exercise is not only good for your body, it’s good for your brain.