Lower IQ tied to heighted risk of schizophrenia, nonaffective psychoses
Lower IQ appears to be associated with low-grade systemic inflammation, as well as an increased risk of developing schizophrenia and other nonaffective psychoses (ONAP) in adulthood, according to a study.
Researchers analysed population-based data on erythrocyte sedimentation rate (ESR) and IQ from 638,213 Swedish men assessed during military conscription between 1969 and 1983. The conscription data were linked to National Hospital Discharge Register for hospitalization with schizophrenia and ONAP.
At baseline, ESR level was 0–3 mm/h in 73.79 percent of participants, 4–6 mm/h in 17.56 percent, 7–10 mm/h in 5.49 percent and ≥11 mm/h in 3.16 percent. Schizophrenia and ONAP developed in 5,398 (0.85 percent) and 5,133 (0.80 percent) individuals, respectively.
Linear and Cox regression analysis showed baseline IQ to be associated with subsequent risk of schizophrenia (adjusted hazard ratio [HR] per 1-point increase in IQ, 0.961; 95 percent CI, 0.960–0.963) and ONAP (adjusted HR, 0.973; 0.971–0.975). There was a dose-response association between higher ESR and lower IQ.
High ESR was associated with a 14-percent increased risk of schizophrenia (adjusted HR, 1.14; 1.01–1.28) and 15-percent lower risk of ONAP (adjusted HR, 0.85; 0.74–0.96), but these effects were specific to one ESR band (7–10 mm/hr).
Familial confounding explained the association between ESR and IQ but not that between ESR and psychoses. Moreover, IQ partly mediated the ESR-psychoses relationships.
The present data suggest that inflammation may increase the risk of schizophrenia by affecting processes involved in cognitive development.