Background and Hypothesis

A sex difference in the clinical presentation of schizophrenia is well known. Males have on average an earlier symptom onset, worse functional capacity, and more negative symptoms. Studies on the neurobiological correlates of psychosis show that brain endocannabinoid system (ECS) is dysregulated in male patients with first-episode psychosis (FEP). We now evaluated whether the brain ECS is also altered in female patients with FEP.

Study Design

In this cross-sectional case–control study, brain CB1R availability was measured in 39 participants, including groups of male and female patients with FEP, and healthy control participants (HC) of similar age and sex (n = 8-11/group). Brain CB1R availability was measured with the selective CB1R radiotracer [¹⁸F]FMPEP-d₂ and positron emission tomography. Arterial input derived distribution volumes (V_T) were extracted from regions of interest (ROI) representing the anterior cingulate cortex, hippocampus, thalamus, and putamen.

Study Results

Within-subjects analyses showed a regionally differential effect of ROI*sex*group (ε = 0.77; F(2.31,80.85) = 4.31, P = .013). Simple effect analyses indicates that male FEP had significantly lower overall CB1R V_T when compared to male HC (F(1,17) = 15.64, p_FWER = 0.018), while female FEP V_T did not differ from female HC (F(1,18) = 0.12, p_FWER = 1). A regionally specific difference of V_T between males and females with FEP (F(3,48) = 3.43, P = .024) did not survive the correction for multiple comparisons (p_FWER = 0.14).

Conclusions

The availability of brain CB1R is differentially altered in males and females with early psychosis. Sex-related neurobiological patterns including the ECS may offer new treatment strategies for alleviating the core symptoms of psychotic disorders in male and female patients.