Neuroplasticity and depression

Neuroplasticity is the brain's ability to reorganize its neural connections in response to experience, learning, and treatment. It is an ongoing process throughout life — unlike what was believed decades ago, when the adult brain was thought to be "fixed."

In depression, neuroplasticity is impaired — particularly in the hippocampus and prefrontal cortex. BDNF (Brain-Derived Neurotrophic Factor), a protein that supports the growth of new neurons and synapses, is reduced in depression. Antidepressants, physical exercise, psychotherapy, and ECT all increase BDNF and promote neuroplasticity.

This discovery changed our understanding of how antidepressants work: the therapeutic effect may not be just about "correcting" neurotransmitters, but about promoting the brain's capacity to reorganize itself and recover functions impaired by the depressive episode. It also explains why the effect takes weeks — synaptic plasticity isn't instantaneous.