Risk of severe mental disorders in adults separated temporarily from their parents in childhood: the Helsinki birth cohort study.

In a large, prospective epidemiological study we tested whether exposure to severe early life stress increases the risk of severe mental disorders in adulthood, and whether childhood socioeconomic background and sex modify these associations. Among the 12,747 participants of the Helsinki Birth Cohort Study, born 1934-1944, 1719 were recorded as separated temporarily from their parents in childhood. The separations took place during World War II when Finnish children were voluntarily evacuated unaccompanied by their parents to temporary foster care abroad (mean age at and length of separation 4.6 and 1.7 years, respectively). Severe mental disorders were identified from the Finnish Hospital Discharge and Causes of Death Registers between years 1969 and 2004. Compared to the non-separated, the separated had higher risks of mental, substance use and personality disorder (P-values ≤ 0.05). The risk of any mental and substance use disorder was, however, highest in the separated and lowest in the non-separated with an upper childhood socioeconomic background; individuals with a lower childhood socioeconomic background showed an intermediate risk regardless of their separation status (P-values for interactions ≤ 0.05). Temporary separation from parents poses a risk of severe mental disorders later in life. Children with an upper childhood socioeconomic background may be particularly sensitive to this type of early life stress, while for children with a lower childhood socioeconomic background it may not add to the risk already associated with lower socioeconomic position in childhood.