10.1016/j.jpsychires.2014.10.011 ; Stress and inflammation are thought to play a role in the risk of developing a psychotic disorder. We aimed to identify stress-related biomarkers for psychosis transition in help-seeking individuals with an at-risk mental state (ARMS). We studied 39 ARMS subjects who were attending an Early Intervention Service. We included a control group of 44 healthy subjects (HS) matched by sex and age. Stressful life events and perceived stress were assessed. Stress-related biomarkers were determined in serum (cortisol, prolactin, C-reactive protein and albumin), plasma (fibrinogen) or saliva (morning cortisol, cortisol awakening response). All ARMS were followed-up at our Unit for at least one year. We divided the ARMS group into two subgroups based on the development of a psychotic disorder (ARMS-P, N=10) or not (ARMS-NP, N=29). ARMS-P reported more stressful life events and perceived stress than HS and ARMS-NP groups. In relation to baseline stress biomarkers, ARMS-P subjects had increased prolactin and lower albumin levels in serum, when compared to ARMS-NP and HS groups. These results did not change when repeated in a subsample of antipsychotic-naïve ARMS subjects. We also found significant differences between groups in the cortisol secretion after awakening. In a multinomial logistic regression adjusting for age, sex and life stress, prolactin was a predictor of psychosis transition whereas albumin levels had a protective effect. Our study underscores the role of stress and stress-related biomarkers (cortisol awakening response, prolactin and albumin) in the pathogenesis of psychosis.