Brain structural changes in mood disorders

Neuroimaging studies allow for the identification of brain structural changes associated with mood disorders and aid in the formulation of neuroanatomical models regarding their pathogenesis. The pattern emerging from the currently available literature suggests that overall structural change in mood disorders is limited and shows a degree of regional and diagnostic specificity. The anterior cingulate cortex (and its subdivisions) is implicated in both bipolar disorder (BD) and major depressive disorder (MDD), whereas reductions in hippocampal volume have been reported consistently only in MDD. Changes in the volume of the amygdala have been noted in both disorders, but there is a degree of inconsistency with regard to the direction of change. Overall, the existing literature is severely limited by small sample sizes, and potentially important sources of variance associated with patients' demographic and clinical features have been insufficiently addressed. Additionally, there is increasing awareness that psychotropic medication may also impact on brain structure. The evidence for this is most robust for lithium and antidepressants; both types of medication are associated with increases in grey matter volume (either global or regional) that have been interpreted as neurotrophic on the basis of preclinical data. Although substantial progress has been made in exploring the structural neuroanatomy of mood disorders, the field would benefit from large-scale studies with prospective, longitudinal designs.