The persistence of developmental markers in childhood and adolescence and risk for schizophrenic psychoses in adult life: a 34-year follow-up of the Northern Finland 1966 birth cohort

Childhood precursors of schizophrenia include multiple abnormalities of development. Continuities between early and subsequent deviance are poorly characterised. We studied associations among premorbid developmental deviance using data at ages 1 year (learning to stand, walk, and speak, attainment of bladder and bowel control) and 16 years (success at school). Generalised linear modelling was used to examine differential linear associations and trends across adult psychiatric diagnoses. In babies who, as adults, suffered schizophrenia or any psychosis, those who learned to stand latest were also more likely to perform poorly at school in both motor and theoretical domains at age 16 when compared with earlier learners. The effect was independent of genetic and perinatal factors. We conclude that the early developmental deviation in the first year of life is associated with lower school performance at age 16. Developmental continuity among children who develop psychoses was stronger than among normal controls and those hospitalized for nonpsychotic psychiatric disorder. These findings are in line with the hypothesis that a neural diathesis is present during postnatal brain development before schizophrenia. This supports the longitudinal dimension and life span models of schizophrenia.