Sex differences in symptomatology in people with psychosis have been studied extensively in recent decades. Although studies have pointed to such differences, to date there is no review that has performed a systematic search and quantitative synthesis. In this paper, we describe the protocol for a pairwise meta-analysis comparing a range of symptom outcome measures between men and women diagnosed with a psychotic spectrum disorder at different stages of the disorder (PROSPERO registration number CRD42021264942). In August 2021 we conducted systematic searches of PsychInfo, PubMed, Web of Science, Scopus and Dialnet to identify observational studies that report data on symptoms for males and females separately. Two independent reviewers will conduct literature searches, select studies, extract data, assess the risk of bias and assess outcome quality. To assess the effect size of all outcome measures, we will conduct pairwise meta-analysis using random-effects models. The quality of studies will be evaluated using a National Heart, Lung and Blood Institute's quality assessment tool and the confidence in the results will be evaluated using the GRADE tool. Meta-regression and sensitivity analyses will be conducted to assess the robustness of the findings. No ethical problems are foreseen. Results from this study will be published in peer-reviewed journals and presented at relevant conferences.

Altered hypothalamus-pituitary-adrenal (HPA) axis function and reduced hippocampal volume (HV) are established correlates of stress vulnerability. We have previously shown an attenuated cortisol awakening response (CAR) and associations with HV specifically in male first-episode psychosis patients. Findings in individuals at ultra-high risk (UHR) for psychosis regarding these neurobiological markers are inconsistent, and assessment of their interplay, accounting for sex differences, could explain incongruent results.

Study participants were 42 antipsychotic-naive UHR subjects (24 men) and 46 healthy community controls (23 men). Saliva samples for the assessment of CAR were collected at 0, 30 and 60 min after awakening. HV was determined from high-resolution structural magnetic resonance imaging scans using a semi-automatic segmentation protocol.

Cortisol measures and HV were not significantly different between UHR subjects and controls in total, but repeated-measures multivariate regression analyses revealed reduced cortisol levels 60 min after awakening and smaller left HV in male UHR individuals. In UHR participants only, smaller left and right HV was significantly correlated with a smaller total CAR (ρ = 0.42, p = 0.036 and ρ = 0.44, p = 0.029, respectively), corresponding to 18% and 19% of shared variance (medium effect size).

Our findings suggest that HV reduction in individuals at UHR for psychosis is specific to men and linked to reduced post-awakening cortisol concentrations. Abnormalities in the neuroendocrine circuitry modulating stress vulnerability specifically in male UHR subjects might explain increased psychosis risk and disadvantageous illness outcomes in men compared to women.