Final answer:
Urban living may increase the risk of schizophrenia due to a combination of environmental and genetic factors. High genetic risk individuals in disturbed environments have a higher incidence of the disorder, highlighting the influence of gene-environment interactions.
Step-by-step explanation:
Urban living likely increases the risk for schizophrenia due to a combination of environmental stressors and genetic predispositions. Studies, such as those conducted by Tienari et al., indicate that adoptees with high genetic risk (biological mothers with schizophrenia) who were raised in disturbed family environments had a markedly higher likelihood of developing schizophrenia or other psychotic disorders compared to those in healthier environments. This evidence underscores the relevance of gene-environment interactions in the development of schizophrenia. Factors such as low vitamin D levels, increased likelihood of perinatal infections, and various socio-environmental stressors associated with urban living may all contribute to the risk. Nonetheless, research has yet to definitively point to these factors as direct causes, suggesting that all of these answers are correct in contributing to the increased risk, rather than a singular factor being responsible.