Preterm Birth and Psychiatric Disorders in Young Adult Life

CONTEXT: Preterm birth, intrauterine growth restriction, and delivery-related hypoxia have been associated with schizophrenia. It is unclear whether these associations pertain to other adult-onset psychiatric disorders and whether these perinatal events are independent. OBJECTIVE: To investigate the relationships among gestational age, nonoptimal fetal growth, Apgar score, and various psychiatric disorders in young adult life. DESIGN: Historical population-based cohort study. SETTING: Identification of adult-onset psychiatric admissions using data from the National Board of Health and Welfare, Stockholm, Sweden. PARTICIPANTS: All live-born individuals registered in the nationwide Swedish Medical Birth Register between 1973 and 1985 and living in Sweden at age 16 years by December 2002 (n=1 301 522). MAIN OUTCOME MEASURES: Psychiatric hospitalization with nonaffective psychosis, bipolar affective disorder, depressive disorder, eating disorder, drug dependency, or alcohol dependency, diagnosed according to the International Classification of Diseases codes for 8 through 10. Cox proportional hazards regression models were used to estimate hazard ratios and 95% CIs. RESULTS: Preterm birth was significantly associated with increased risk of psychiatric hospitalization in adulthood (defined as ≥16 years of age) in a monotonic manner across a range of psychiatric disorders. Compared with term births (37-41 weeks), those born at 32 to 36 weeks' gestation were 1.6 (95% CI, 1.1-2.3) times more likely to have nonaffective psychosis, 1.3 (95% CI, 1.1-1.7) times more likely to have depressive disorder, and 2.7 (95% CI, 1.6-4.5) times more likely to have bipolar affective disorder. Those born at less than 32 weeks' gestation were 2.5 (95% CI, 1.0-6.0) times more likely to have nonaffective psychosis, 2.9 (95% CI, 1.8-4.6) times more likely to have depressive disorder, and 7.4 (95% CI, 2.7-20.6) times more likely to have bipolar affective disorder. CONCLUSIONS: The vulnerability for hospitalization with a range of psychiatric diagnoses may increase with younger gestational age. Similar associations were not observed for nonoptimal fetal growth and low Apgar score.