Schizophrenia is a disorder where at least some risk factors operate very early in life, even though psychotic symptoms generally first appear in early adulthood. These early events are suggested by the subtle developmental (motor, emotional, cognitive, behavioural and physical) abnormalities, along with increased markers of prenatal neurological disruption (such as increased minor physical anomalies), which are often present in apparently healthy individuals who later develop psychosis.
It is considered that subtle alterations in brain development caused by genes and/or early environmental hazards, such as infection, obstetric complication or malnutrition (such as low perinatal vitamin D) play a role in projecting some individuals on a trajectory toward schizophrenia.
Children destined to develop schizophrenia in adulthood tend to have delayed milestones and subtle neuromotor and cognitive impairments (particularly in coordination and language). These neuro-cognitive problems may be either associated with or lead to difficulties in interpersonal relation and the development of odd or paranoid ideas.
This early developmental deviance may then be compounded by maturational brain changes during adolescence, which result in a lability of the dopaminergic response to stress. As a result the individual is more susceptible to (and indeed may selectively expose him/herself to) certain stresses during adolescent or adult life, such as abuse of drugs and social adversity, especially isolation.