Exploring pathways to psychosis:: Childhood trauma as the invisible backpack

Abstract

Schizophrenia and related psychotic disorders have a severe impact on the lives of patients and the people close to them. Psychotic symptoms include hearing voices that others cannot hear, and the conviction that others have bad intentions towards you. These symptoms can also occur in other disorders such as bipolar disorder, but also Parkinson's disease or hearing loss. Moreover, we know that healthy individuals can also have frequent psychotic experiences such as hearing voices – also known as auditory verbal hallucinations. An important risk factor for the development of psychotic experiences, in patients as well as healthy individuals, is childhood trauma. For example, patients with a psychotic disorder are almost three times more likely to have been exposed to childhood trauma compared to controls. This dissertation describes potential pathways by which childhood trauma is linked to the development of psychotic experiences later in life. We started by investigating the prevalence of auditory hallucinations in the general population. By combining the results of 25 studies in a meta-analysis, our estimations are based on 84 711 individuals. We found that auditory hallucinations were reported by almost 10% of the general population during lifetime. Notably, prevalence rates were higher in children and adolescents compared to adults and elderly. These results disprove the popular notion that psychotic experiences are rare and invariably indicative of full-blown psychosis, which can help in de-stigmatizing these phenomena in general, and psychotic illness in particular. In our subsequent studies, we identified several pathways that together with childhood trauma could mediate the effect childhood trauma may have to induce psychotic experiences. Increased levels of neuroticism, reduced executive functioning, gray matter loss in the frontal and insular regions and maladaptive coping with stressful events encountered later in life, are potential mechanisms by which childhood trauma may increase the risk for developing psychotic experiences and even full-blown psychosis. Future exploration, ideally in longitudinal datasets, is necessary to identify the pathways that link a history of childhood trauma to the development of psychotic experiences and psychosis later in life and, importantly, why some individuals pass the psychosis threshold while others do not.