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. 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 as it develops. The interactions of these risk factors are intricate, as numerous and diverse medical insults from conception to adulthood can be involved. 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.

A genetic predisposition on its own, without superimposed environmental risk factors, is not thought to give rise to schizophrenia. 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.

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. Estrogen seems to have a dampening effect on dopamine receptors.