A team of Scottish researchers (Perrin et al., 2012) have produced evidence that ECT decreases connectivity in the brain of depressed patients, leading to a reduction in symptoms. They used fMRI (functional magnetic resonance imaging) to scan the brains of nine patients, all of whom had severe clinical depression and had not responded to drug therapy. Each received ECT for two sessions per week, an average total of 8 treatments. They were scanned before ECT was applied, and then again afterwards. Using a new mathematical analysis they were able to determine to what extent 25,000 different brain areas ‘communicated’ with each other.  This indicated changes after ECT in the left dorsolateral prefrontal cortical region; connectivity was reduced and this was associated with improvements in depressive symptoms.

When a patient has depression, parts of the brain that control mood and those involved in concentration and thinking have an overactive connection. So it appears that ECT ‘turns down’ these connections leading to improved mood.