https://www.ncbi.nlm.nih.gov/pubmed/27174729

Neuroplasticity is a real buzz word in neuroscience at the moment and describes the way in which our brains reorganise themselves by forming new neural connections throughout life. Neuroplasticity allows the neurons (nerve cells) in the brain to compensate for injury and disease and to adjust their activities in response to new situations or to changes in their environment. Merzenich is one of the main scientists over the past 30 years who has transformed the field of neurology by overturning the dogma that our mental abilities are immutable and fixed early in life. Cognitive impairment associated with neurological maladies, such as strokes and traumatic brain injury, were once considered to be largely untreatable. Normal age-related cognitive decline was also considered to be unavoidable. But Merzenich and other researchers have shown that the brain can physically remodel itself and that the brain we are born with is not a fixed structure with a set of weaknesses and strengths at all.

Depression is associated with both low serum Brain Derived Neurotrophic Factor (BDNF) and elevated levels of serum cortisol. The linked study here examined the association between serum BDNF and cortisol levels in patients with depression treated with antidepressants, yoga therapy, and both. 54 people diagnosed with depression took part in the study receiving anti-depressants only, yoga therapy only, or yoga with antidepressants. Both BDNF and cortisol levels were measured before the intervention and three months subsequently. A significant negative correlation was observed between change in BDNF (pre-post) and cortisol (pre-post) levels in the yoga-only group. The author concluded that yoga may facilitate neuroplasticity through stress reduction in depressed patients. Further studies are needed, however. to confirm these findings and to delineate the pathways for these effects.