The biopsychosocial model of schizophrenia and cancer: Unraveling the etiopathogenesis of complex diseases

Schizophrenia and cancer are complex disorders causing severe impairment and premature mortality. They both include a wide range of different illnesses, with different symptoms, course, and outcome. Although the causes of schizophrenia remain largely unknown, research into the etiopathogenesis of cancer has led to clarify its main genetic and environmental factors [1]. Our understanding of the etiopathological mechanisms of schizophrenia is still far from being conclusive. It is now conceptualized as a neurodevelopmental disorder, lying on a continuum, from mild psychotic experiences observed in the general population to frank psychotic episode. Our diagnosis of schizophrenia is mainly based on non-observable signs and symptoms reported by patients, that are associated with various degrees of disability and that last for at least 6 months [2]. One of the most accepted theories of schizophrenia is the stress-vulnerability model [3], according to which psychotic symptoms would be based on a genetic or biological vulnerability, and triggered by stressful environmental factors [4]. This model is based on the biopsychosocial model of modern medicine. Cancer follows a similar pathway. Several genetic loci have been identified to be responsible for the liability to the illness, and several biological (e.g., hormones), social (e.g., education), environmental (e.g.,