Early Childhood IQ Trajectories in Individuals Later Developing Schizophrenia and Affective Psychoses in the New England Family Studies

Individuals who develop schizophrenia in adulthood exhibit, on average, deficits in childhood cognition relative to healthy controls. However, it remains unclear when in childhood such deficits emerge and whether they are stable across childhood or change (increase or decrease) across development. Importantly, whether the trajectory of childhood cognition differs among youth who later develop affective psychoses (AP) vs schizophrenia as adults remains unresolved. Subjects in the Collaborative Perinatal Project were administered the Stanford-Binet IQ test at age 4 and the Wechsler Intelligence Scale for Children at age 7. A total of 9809 (54.7%) participants in the New England Study sites were tested at both ages, including 37 who later developed schizophrenia spectrum psychoses (SSP) and 39 who later developed AP. Logistic regression models examined the association of level of and change in childhood IQ and later SSP or AP. Lower overall childhood IQ was associated with higher risk of SSP. Additionally, there was a small mean increase in IQ in the SSP group relative to a mean decrease in the control group from age 4 to 7 such that positive change in IQ was significantly associated with a higher risk of SSP. Neither overall level nor change in IQ was associated with risk of AP. The results are consistent with neurocognitive impairment throughout early childhood specifically for children who later develop schizophrenia, affirming the theory of atypical neurodevelopment in premorbid schizophrenia.