Prenatal smoking exposure and the risk of psychiatric morbidity into young adulthood.

CONTEXT

Prenatal smoking exposure modulates brain development, which may deviate mental development of the offspring.

OBJECTIVE

To study the effects of prenatal smoking exposure on psychiatric morbidity and mortality among Finnish young adults by means of population-based longitudinal register data.

DESIGN

Information on maternal smoking as reported by the mothers (0, <10, or >10 cigarettes a day) and other background factors (maternal age and parity and child's sex, gestational age, birth weight, and 5-minute Apgar score) was derived from the Finnish Medical Birth Register. Information on children's psychiatric diagnoses related to outpatient visits (1998-2007), children's inpatient care (1987-2007), and mothers' psychiatric inpatient care (1969-1989) was derived from the Finnish Hospital Discharge Register. Information on deaths and their causes for the children (1987-2007) was received from the Cause-of-Death Register.

SETTING

Population-based study of all singletons born in Finland from 1987 to 1989 with information on prenatal smoking exposure. Patients The source population included all singleton births in Finland from January 1, 1987, through December 31, 1989 (n = 175 869), excluding children with major congenital anomalies (3.1%) and children who died during the first week of life (0.3%).

MAIN OUTCOME MEASURES

Psychiatric morbidity and mortality.

RESULTS

The prevalence of maternal smoking was 15.3%. The risk of psychiatric morbidity was significantly higher in the exposed children than in the unexposed children. Among the offspring of mothers who smoked fewer than 10 cigarettes a day, 21.0% had any psychiatric diagnoses (adjusted odds ratio [OR], 1.53 [95% confidence interval (CI), 1.47-1.60]) compared with 24.7% among those of mothers who smoked more than 10 cigarettes a day (1.85 [1.74-1.96]) and 13.7% in the unexposed children (the reference group). The risk was significantly increased for most of the psychiatric diagnoses. The strongest effects were in psychiatric disorders due to psychoactive substance use and in behavioral and emotional disorders. The risk of mortality was significantly higher in children exposed to more than 10 cigarettes a day (OR, 1.69 [95% CI, 1.31-2.19]) compared with unexposed children.

CONCLUSION

Prenatal smoking exposure is associated with an increased risk of psychiatric morbidity, whereas prenatal exposure to more than 10 cigarettes a day increases the risk of mortality in childhood, adolescence, and young adulthood.