The role of cerebellum in unipolar and bipolar depression: a review of the main neurobiological findings.

Evidences from studies on patients with overt cerebellar diseases as well as on healthy individuals suggest a possible role for the cerebellum in cognition, mood and behaviour. The aim of the present study is to review those neuroimaging studies examining the cerebellum in Bipolar Disorder (BD) and Major Depressive Disorder (MDD) and to illustrate a possible role of cerebellum in their pathophysiological mechanisms. Cellular and molecular findings from post mortem studies such as mitochondria abnormalities, brain-derived neurotrophic factor and its high affinity receptor tyrosine kinase B, transcription factor specificity protein 4, the glial fibrillary acidic protein have also been reviewed. In total 28 studies have been included in the review; among these, 12 studies were related to structural and functional neuroimaging of cerebellum in BD, 13 studies to structural and functional neuroimaging in MDD and 4 studies to cellular and molecular issues. This wealth of evidence from contemporary studies, indicating that the cerebellum (vermis in particular) is engaged in the modulation of emotional processing, provides strong support for the clinical relevance of cerebellar-limbic connections, and is in agreement with earlier clinical and electrophysiological studies that lead to the indication of the cerebellum as an "emotional pacemaker".