Posterior fossa abnormalities in major depression: a controlled magnetic resonance imaging study.

High-field magnetic resonance (MR) images were used to study posterior fossa morphology in 27 patients with major depression and 36 normal control subjects. Depressed patients demonstrated smaller brain stem and cerebellar vermis than controls. These differences were highly significant for the anterior cerebellar vermis and medulla. There was also a striking age-related decline in midbrain size in depressed patients as well as in controls. Our results are consistent with several lines of evidence implicating a role for the cerebellar vermis in affective disorders and, in addition, provide the first MR documentation of the differential effects of aging on posterior fossa morphology in normal subjects compared with patients with major depression.