A review of the literature on primarily magnetic resonance imaging (MRI) scans of patients with affective disorders is presented. Several studies have indicated an increased ventricle/brain ratio and other signs of cerebral atrophy, as well as an increased frequency of lesions (so-called signal hyperintensities) in the brains of unipolar and bipolar patients. This notion is strongly supported by two meta-analyses performed in the present study. The lesions are often localized in the frontal lobes and the basal ganglia, indicating a defective basal ganglia/frontal circuit, and are correlated with the degree of cognitive impairment seen in these conditions. No studies have indicated that psychoactive drugs or electroconvulsive therapy (ECT) might cause the lesions, but on the other hand they can probably increase the risk of delirium complicating the treatment.