Flattened cortisol awakening response in chronic patients with schizophrenia onset after cannabis exposure

Cannabis may play a causal role in the onset of some schizophrenia cases; however, the biological vulnerability that predisposes some individuals to develop schizophrenia after exposure to cannabis is not known. According to the diathesis-stress pathogenetic model, it is likely that the endogenous stress response system, including the hypothalamus-pituitary-adrenal (HPA) axis, could be involved. Therefore, we investigated the saliva cortisol awakening response (CAR) of 16 patients with schizophrenia onset after the exposure to cannabis (Can+) as compared to 12 patients with schizophrenia onset without cannabis exposure (Can-) and to 15 healthy controls. The CAR was assessed by collecting saliva samples at awakening and after 15, 30 and 60 min. As compared to healthy controls, Can+ schizophrenia patients exhibited significantly enhanced baseline saliva cortisol levels and a flattened CAR. No significant abnormality in both baseline cortisol levels and CAR was detected in Can- schizophrenia patients. These findings demonstrate a dysregulation of the HPA axis in chronic schizophrenic patients whose illness started after cannabis exposure but not in those with an illness onset without cannabis exposure. Further studies need to clarify whether this HPA dysregulation is a part of the biological background underlying the increased risk to schizophrenia after exposure to cannabis.