A new study from Karolinska Institutet and Johns Hopkins University in Baltimore, USA, shows that adopted children from a biological family with experience of suicide were more likely to themselves attempt suicide if their adoptive mother had also been treated for a psychiatric disorder. The results, which are presented in the scientific periodical The American Journal of Psychiatry, suggest that the genes can be affected by environmental factors, according to the researchers.
It is known from previous research that a family that has already suffered a suicide is at risk of a recurrence. Suicide appears to be more likely in those who are exposed to suicidal behaviour in the family as a child or teenager than as a young adult. Suicidal behaviour is also slightly more likely in adults if, as children, their mother - rather than their father - had attempted suicide. To ascertain whether this increased risk is genetically or environmentally determined researchers at Karolinska Institutet and Johns Hopkins studied early-adopted children with an enhanced family-related suicide risk but, as adoptees, no exposure to a suicidal act by a biological parent.
Their results show that the likelihood of an adopted child attempting suicide later in life was unaffected if there was only one biological parent who had committed or attempted suicide or if the adoptive parent had been receiving psychiatric treatment before the child turned 18; however, there was a four-fold risk if a biological parent displayed suicidal behaviour and the adoptive mother had been in psychiatric care.
"We see this as a sign of hereditary-environment interaction, whereby the biological or genetic inheritance can be influenced by environmental factors in early childhood," says investigator Professor Bo Runeson at the Department of Clinical Neuroscience, Karolinska Institutet. "Identifying and treating psychiatric disorders in parents is one possible way to prevent a predisposition for suicidal behaviour being passed down to the next generation."
The study was carried out using data from Swedish registries dating from 1973 to 2003, and is a retrospective cohort study of 2,516 individuals with a biological parent who had committed or attempted suicide, and 5,875 individuals with a biological parent who had undergone psychiatric treatment but not attempted suicide. The researchers studied these groups to ascertain whether an adoptive parent in psychiatric care moderated the incidence of attempted suicide in adopted children.
The interaction of parental history of suicidal behavior and exposure to adoptive parent's psychiatric disorders on adoptee suicide attempt hospitalizations. Wilcox HC, Kuramoto SJ, Brent D, Runeson B. American Journal of Psychiatry, online in advance of publication 7 February 2012 , doi: 10.1176/appi.ajp.2011.11060890.