Risk of sudden infant death syndrome with parental mental illness

Context: Sudden infant death syndrome is the leading cause of postneonatal death in developed countries. Little is known about risks linked with parental mental illness per se or how such risks are modified by specific psychiatric conditions and by maternal vs paternal psychopathological abnormalities. Objective: To investigate cause-specific postneonatal death, including sudden infant death syndrome, in infants whose parents had been admitted as psychiatric inpatients. Design: National cohort study. Setting: The entire Danish population. Patients: All of the singleton live births registered from January 1, 1973, to December 31, 1998. Linkage to the national psychiatric register enabled identification of all of the parental admissions from April 1, 1969, onward. Main Outcome Measure: All of the cases of sudden infant death syndrome in the postneonatal period classified via national mortality registration between January 1, 1973, and December 31, 1998. Results: Psychiatric admission history in either parent doubled the risk of sudden infant death syndrome, but there was no difference in risk whether infants were exposed to maternal or paternal admission. Risk was particularly high if both parents had been admitted for any psychiatric disorder (relative risk, 6.9; 95% confidence interval, 4.1-11.6). Among specific parental disorders, the greatest risk was associated with admission for alcohol-or drug-related disorders (mothers: relative risk, 5.0; 95% confidence interval, 3.4-7.5; fathers: relative risk, 2.5; 95% confidence interval, 1.7-3.8). Contrary to prior expectation, parental schizophrenia and related disorders did not confer higher risks than other parental disorders that resulted in admission. Conclusions: Infants whose parents have been admitted for psychiatric treatment are at greater risk for sudden infant death syndrome. However, risks may be lower than previously thought with maternal schizophrenia and related disorders. Clinicians should be aware of particularly high risks if both parents have received any psychiatric inpatient treatment or if either parent (but the mother especially) was admitted with an alcohol- or drugrelated disorder.