Aim: Various forms of social adversity have been implicated in the development and emergence of psychosis. However, how and when these events exert their influences are not clear. In this paper, we attempt to examine these putative psychosocial factors and place them in a temporal context and propose a neurobiological mechanism linking these factors. Methods: Medline databases were searched between 1966 and 2007 followed by the crosschecking of references using the following keywords: psychosocial, stress, stressors, life events, psychological, combined with psychosis and schizophrenia. Results: While some findings are conflicting, there are a number of positive studies which suggest that factors like prenatal stress, urban birth and childhood trauma accentuate the vulnerability for schizophrenia and other psychoses while other factors like life events, migration particularly being a minority group, and high expressed emotions, which occur later in the vulnerable individual may move the individual towards the tipping point for psychosis. Conclusion: Overall, there is evidence to implicate psychosocial factors in the pathophysiology of schizophrenia. These factors may act via a common pathway, which involves stress-induced dysregulation of the HPA axis and the dopaminergic systems. To establish the causal relationship of the various factors would require prospective studies that are adequately powered.
The architecture of the neurobiology of schizophrenia is complex: it comprises an inherited vulnerability with multiple genes involved, and its interaction with a number of environmental factors. That the onset of psychosis typically occurs during late adolescence and early adulthood is suggestive that additional factors play significant roles along the trajectory from a vulnerability state to the onset of schizophrenia. The current view about schizophrenia is that this represents a progressive developmental patho-physiology of the illness that may result from several factors working individually, or in combination.
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