The incidence of schizophrenia in the context of growing up in urbanised vs. green areas – a narrative review

Abstract

The neurodevelopmental theory of schizophrenia describes multiple risk factors of this serious mental disorder. These include genetic factors that generally have biological roots, as well as factors related to the upbringing in a specific environment during childhood and adolescence of a person who will develop schizophrenia in adulthood. The neurodevelopmental hypothesis also implies the existence of protective factors. The paper discusses selected environmental risk factors and protective factors of schizophrenia in the context of ecopsychiatry. Urbanicity has for decades been a factor indicated as one that increases the risk of schizophrenia. Contemporary research helps understand how growing up in an urban environment affects brain development, with a particular focus on grey matter volume changes in the dorsolateral prefrontal cortex and the perigenual anterior cingulate cortex. The impact of air pollution as a risk factor for schizophrenia is also the subject of discussions. Exposure to outdoor air pollutants containing particulate matter and ultrafine particulate matter, gases, organic compounds, and metals can lead to neurotoxicity and neuropathology. Air pollution can affect the brain through such mechanisms as inflammation and oxidative stress. On contrary, higher exposure to green spaces has been suggested to reduce the incidence of schizophrenia. Some research indicates a dose-response association between the level of exposure to green space in childhood and a lower risk of developing schizophrenia in the future. The presented review of selected publications indicates that exposure to a certain environment in childhood and adolescence modulates the risk of schizophrenia. Environments heavily transformed by human activity (urbanisation) and characterised by a high level of chemical contamination (toxins, air pollution, smog) are a risk factor for schizophrenia. Protective factors, on the other hand, include direct contact with the natural environment from childhood through adolescence to adulthood.