• bipolar disorder;
  • brain morphology;
  • first episode;
  • magnetic resonance imaging;
  • meta-analysis

Objectives:  To perform a comprehensive quantitative analysis of the existing magnetic resonance imaging (MRI) studies of the brain conducted on patients with first-episode bipolar disorder (BD).

Methods:  A systematic search was performed of MRI studies that reported quantitative measurements of brain volumes of first-episode bipolar patients and healthy controls. Four meta-analyses were performed for four cerebral regions.

Results:  Significant overall effect sizes were demonstrated, with a reduction detected in patients with BD for total intracranial and white matter volumes, but not for gray matter and whole brain volumes.

Conclusions:  The available MRI literature indicates that specific structural brain abnormalities are already present in first-episode bipolar patients. These do not overlap with those emerging from previous meta-analyses performed in patients with chronic BD. These findings support the hypothesis of different patterns of changes in brain morphology over the time course of bipolar disorder.