Hippocampal volume in affective and non-affective psychosis.

Hippocampal volume change in non-affective psychotic disorders begins in the anterior region and spreads to the posterior region as the illness progresses. It is unclear whether similar hippocampal volume changes are present in affective psychosis. Here, we test the hypothesis that anterior and posterior hippocampal volumes are differentially affected in affective psychosis. We also investigated the prevalence of a marker of atypical hippocampal development, incomplete hippocampal inversion (IHI), and its impact on hippocampal volume in affective psychosis. We analyzed total, anterior, and posterior hippocampal volumes using automated segmentation of structural MRI data from 103 affective psychosis, 242 non-affective psychosis, and 214 healthy control individuals. Compared to healthy participants, individuals with affective psychosis exhibited smaller posterior hippocampal volumes. The two psychosis patient groups did not differ significantly in total or regional hippocampal volumes. IHI prevalence and severity were greater in individuals with non-affective and affective psychosis. Our findings suggest hippocampal volume is reduced in the posterior, but not anterior, hippocampus in affective psychosis and that IHI may be a marker for an increased risk of developing psychosis.