Suicidal behavior in twins: a replication

Objective: Our two previous reports showed that monozygotic (MZ) twins were significantly more concordant for both completed suicide and attempted suicide than dizygotic (DZ) twins. We wished to replicate the finding that MZ co-twins showed greater concordance for suicidal behavior. Method: We collected a new series of 28 twin pairs in which one twin had committed suicide. Results: We found that 4 of the 13 MZ twin pairs were concordant for suicidal behavior compared with 0 of the 15 DZ twin pairs (P=0.035). Conclusions: These data confirm our previous reports that MZ co-twins show greater concordance for suicidal behavior than DZ co-twins, consistent with genetic influence.