Postpartum psychosis (PP) is an uncommon psychiatric condition that, if untreated, can have devastating consequences. The underlying biology of PP remains poorly understood. To investigate the neurobiological mechanisms of PP, this study measured neuromelanin (NM)-sensitive magnetic resonance imaging (MRI) signal intensity, a marker of dopamine turnover, in the midbrain of women with a prior history of PP (n = 30) and a group of demographically-matched healthy control (HC) women (n = 24). NM-MRI signal intensity in dopamine-rich midbrain areas, the substantia nigra (SN) and ventral tegmentum area (VTA), as well as whole-brain resting-state functional connectivity of the bilateral SN, were measured and compared across the two groups. Significantly elevated levels of NM-MRI signal in the SN and VTA were observed in the PP (vs. the HC) group, and these elevations were significantly correlated with levels of residual, subclinical psychotic symptoms within the PP group. Additionally, significant decreases were observed in the PP (vs HC) group in the functional connectivity of the bilateral SN to multiple subcortical regions; these decreases were associated with levels of SN NM-MRI signal and subclinical psychotic symptoms. This study provides the first evidence for elevated midbrain NM-MRI signal in women with a history of PP. Also, this abnormality was linked to the presence of residual subclinical psychotic symptoms and altered connectivity of the SN. Future studies will determine whether NM-MRI can serve as a useful tool for screening women for risk for PP.
McKenna et al. (2026) studied this question.