Another important issue in the etiology of schizophrenia is the relationship between risk factors and age-at-onset. Age-at-onset of frank psychotic symptoms is highly variable – ranging from childhood to late adulthood.
What factors influence the age of onset of psychosis?
As previously noted, onset is generally earlier in males than in females. Furthermore, those with a family history of schizophrenia tend to have an earlier age of onset than cases with less genetic risk, regardless of their sex. Also, the relatives of late-onset psychosis cases seem to carry less genetic loading for schizophrenia and are at higher risk for affective disorders. Obstetric complications may also be associated with early onset, as are other indicators of aberrant neurodevelopment, such as premorbid cognitive and behavioral deficits, minor physical anomalies, smaller brains, and larger cerebral ventricles.
In sum, neurodevelopmental impairment is most marked in early-onset schizophrenia, but becomes less obvious with increasing age of onset. This, as well as other characteristics – such as different symptom profiles based on age-at-onset - has led to the question of whether schizophrenia is comprised of a number of syndromes, perhaps similar to other etiologically complex disorders such as diabetes.