It's estimated that around 10% of people will at some point in their lives suffer from depression. Neuroimaging studies reveal that many brain circuits that normally regulate mood are disregulated in depression. In depression the amygdala is overactive and responds excessively to negative events. Response to emotional stimuli these areas include the medial prefrontal cortex the nucleus accumbens the hippocampus and the insula. Depressed people are more susceptible to stress which can cause physical changes in the brain including atrophy of the hippocampus.
This and other changes in depressed people may cause inappropriate responses to emotional events. The medial prefrontal cortex is involved in regulating how strongly we react to emotional stimuli. Treatments such as antidepressant drugs, cognitive behavioral therapy, physical activities, and electroconvulsive therapy affect the structure and function of these and other brain regions.