# Mapping cerebellar subregional volumes and heterogeneity in schizophrenia spectrum disorders and violence

## TL;DR

This study explores how cerebellar structure differences are linked to schizophrenia and violent behavior, finding distinct patterns in subregional volumes.

## Contribution

The study introduces novel heterogeneity analyses to uncover cerebellar deviations in schizophrenia and violence.

## Key findings

- SSD-V and SSD-NV showed decreased grey matter in posterior cerebellar hemispheres and vermal regions.
- SSD-V had significant volume reductions in the right Crus I and Vermis IX.
- NPV showed extreme deviations in posterior cerebellum and vermis in over 10% of cases.

## Abstract

Cerebellar abnormalities have been linked to schizophrenia and aggressive behaviour. Subregional cerebellar morphology reflects structural organization and function and show great heterogeneity, which may be linked to shared or distinct underlying mechanisms of violence and psychosis but remain unexplored in these marginalized groups. Total and subregional cerebellar volumes were estimated from 3 T MRI scans from persons with schizophrenia spectrum disorders without (SSD-NV; n = 107) or with (SSD-V; n = 36) a history of severe violence, violent offenders without schizophrenia (NPV; n = 20), and 411 healthy controls. Group difference analyses by GLMs were complemented by novel heterogeneity analyses using pre-trained models and norm-charts of lifespan cerebellar volumes to assess individual deviation patterns. We found decreased grey matter volumes in the posterior cerebellar hemispheres and the vermal regions in both SSD-V and SSD-NV, but with a different subregional distribution. Specifically, SSD-V showed differences in the right Crus I (p = .045, Cohen’s d = .62) and Vermis IX (p < .001, Cohen’s d = .81) in the groupwise comparisons. In addition, individual-level extreme negative deviations were detected in the Vermis IX region in 11% of SSD-V and in some subregions of the posterior cerebellum and the vermis in > 10% of NPV. By applying novel analytical tools, we report different patterns of cerebellar subregion volume reductions associated with violence in individuals with or without schizophrenia spectrum disorders. The partly converging results from the group comparisons and the normative modelling analyses demonstrate the usefulness of complemental methodological approaches to disentangle the complex biological associations between violence and psychosis.