Normal sexual dimorphism in theory of mind circuitry is reversed in Schizophrenia

The ability to mentalize, or theory of mind (ToM), is sexually dimorphic in humans and impaired in schizophrenia. This sex-stratified study probed cognitive (indexed by intelligence) and affective (indexed by olfactory tasks) contributions to ToM performance in 37 individuals with schizophrenia and 31 healthy controls. The schizophrenia group showed impairments in mental state identification and inferring intentions compared to controls. Higher intelligence was correlated with mental state identification and inferring intentions in healthy females, whereas better smell identification was associated with mental state identification in healthy males. Conversely, higher intelligence was associated with mental state identification and inferring intentions in schizophrenia males, while better smell identification was correlated with mental state identification in schizophrenia females. These findings suggest that for ToM circuitry, the cognitive influences in healthy females and affective influences in healthy males are reversed in schizophrenia and may be displaced to lower circuitries by disease pathology. Symptom associations with emotion and cognition are also dimorphic, plausibly due to similar pathology superimposed on normal sex-specific circuitries. Males appear to rely on limbic processing for ToM, and disruption to this circuitry may contribute to development of negative symptoms. These findings highlight the importance of utilizing sex-stratified designs in schizophrenia research.