Social Stress and Psychosis Risk: Common Neurochemical Substrates?

Environmental risk factors have been implicated in the etiology of psychotic disorders, with growing evidence showing the adverse effects of migration, social marginalization, urbanicity, childhood trauma, social defeat, and other adverse experiences on mental health in vulnerable populations. Collectively, social stress may be one mechanism that could link these environmental risk factors. The exact mechanism(s) by which social stress can affect brain function, and in particular the molecular targets involved in psychosis (such as the dopaminergic (DA) system), is (are) not fully understood. In this review, we will discuss the interplay between social environmental risk factors and molecular changes in the human brain; in particular, we will highlight the impact of social stress on three specific neurochemical systems: DA, neuroinflammation/immune, and endocannabinoid (eCB) signaling. We have chosen the latter two molecular pathways based on emerging evidence linking schizophrenia to altered neuroinflammatory processes and cannabis use. We further identify key developmental periods in which social stress interacts with these pathways, suggesting window(s) of opportunities for novel interventions. Taken together, we suggest that they may have a key role in the pathogenesis and disease progression, possibly provide novel treatment options for schizophrenia, and perhaps even prevent it.