Risk factors of schizophrenia

Schizophrenia is a neurodevelopmental disorder with no precise or single cause. Schizophrenia is thought to arise from multiple mechanisms and complex gene–environment interactions with vulnerability factors.^[1][2] Risk factors of schizophrenia have been identified and include genetic factors, environmental factors such as experiences in life and exposures in a person's environment, and also the function of a person's brain at it develops.^[3] The interactions of these risk factors are intricate, as numerous and diverse medical insults from conception to adulthood can be involved.^[4] Many theories have been proposed including the combination of genetic and environmental factors may lead to deficits in the neural circuits that affect sensory input and cognitive functions.^[5]

A genetic predisposition on its own, without superimposed environmental risk factors, is not thought to give rise to schizophrenia.^[4][6] Environmental risk factors are many, and include pregnancy complications, prenatal stress and nutrition, and adverse childhood experiences. An environmental risk factor may act alone or in combination with others.^[7]

Schizophrenia typically develops between the ages of 16–30 (generally males aged 16–25 years and females 25–30 years); about 75 percent of people living with the illness developed it in these age-ranges. Childhood schizophrenia (very early onset schizophrenia) develops before the age of 13 years and is quite rare. On average there is a somewhat earlier onset for men than women, with the possible influence of the female sex hormone estrogen being one hypothesis and socio-cultural influences another.^[8] Estrogen seems to have a dampening effect on dopamine receptors.^[9]