Exercise is beneficial in the treatment of depression on various occasions over the years. The processes underlying this effect, on the other hand, have remained a mystery. A new study published in the journal Frontiers in Psychiatry throws new light on the riddle. Exercise increased neuroplasticity in depressed people, according to the study.
Neuroplasticity can be thought of as the brain’s ability to remodel itself in response to environmental changes. It is a complex phenomenon, largely controlled 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 connections becoming stronger and others weaker as new circuitry is laid down and communication pathways between brain areas change. Antidepressant medicines are thought to alleviate depression by increasing neuroplasticity, and novel brain-stimulation treatments for depression, such as repeated transcranial stimulation (rTMS), appear to do the same thing by sending tiny electrical impulses directly to the cortex.
The study involved 41 people who had been admitted to the hospital for depression. They were divided into two groups once they had recovered enough from their symptoms to participate in the study. One group engaged in exercise groups three days a week for three weeks, whereas the control group played (sedentary) games that required them to use reasoning and deduction to solve puzzles three days a week.
The level of neuroplasticity of each subject was measured before and after their three-week interventions using a model of "brain training" called the paired-association stimulation (PAS) technique. PAS involves electrically stimulating the nerve at the base of the thumb while also employing an rTMS device to send magnetic impulses to the motor cortex area that controls the thumb muscles, resulting in a transient flexing of the thumb muscles. In around 30 minutes, this dual stimulation "trains" the underlying motor cortex. It increases its sensitivity to magnetic impulses, which might cause the thumb to move at lower and lower intensities. Neuroplasticity is supposed to be measured by the robustness of the reaction to the PAS "training" ("PAS effect").
The self-reported Beck Depression Inventory-II and the clinician-administered Hamilton Depression Rating Scale were used to assessing the subjects' depression levels before and after their treatments. There was a direct link between the PAS effect and the degree of depression at baseline in both groups. The PAS effect was smaller in subjects with a higher depression level, indicating that the brain had less neuroplasticity.
The group that exercised had considerably lowered depression scores at the end of the trial than the group that engaged in sedentary activities. Their PAS effect scores were also higher, indicating enhanced neuroplasticity. There was a direct link between depression level and the PAS effect. The PAS effect revealed that the participants whose depression had recovered the most had the highest development in neuroplasticity.
Exercise has been proven to increase metabolism and oxygenation, alter neurotransmitters, and enhance the production of neurotrophic proteins like BDNF in the brain, and the authors argue that these are some processes through which exercise enhances neuroplasticity. Exercise programs should be included in the therapy of depression, according to the researchers.