PRL and schizophrenia: While many other factors appear to influence circulating testosterone levels in males (e.g., ethnicity, BMI, smoking, marital status, fatherhood, seasonality, and in men with schizophrenia: antipsychotics), our samples were well matched on age and ethnicity and we found no significant group differences in testosterone or prolactin levels, suggesting that these variables are unlikely to account for our findings.