SUICIDE ATTEMPTS IN TWINS WHOSE CO-TWINS DEATHS WERE NON-SUICIDES

Familial similarity for suicidal behavior has been interpreted by psyc hosocially oriented researchers as reflecting extreme grief following loss. This view would anticipate a higher frequency of attempted suici de among bereaved MZ than DZ twins (regardless of cause of death), giv en their generally increased social closeness. Alternatively, support for a genetic influence on suicidal behavior has been provided by find ings of greater concordance among monozygotic (MZ) than dizygotic (DZ) twins, and among biological than adoptive relatives. This approach pr edicts that the occurrence of suicidal attempts among bereaved MZ and DZ twins whose co-twins deaths were non-suicides should not differ and should be low in frequency, given an absence of predisposing genetic factors. Attempted suicide was compared in 166 MZ and 79 DZ twins whos e co-twins' deaths were non-suicides. Suicidal attempts (during the fi rst two months following the loss) were recalled by 3 MZ twins (1.8%) and by 3 DZ twins (3.7%), a difference that was not significant. The p resent study, together with previous twin and adoption studies, suppor ts the view that concordance for suicide among family members reflects a common genetic predisposition to suicidal behavior.