Decrease in grief intensity for deceased twin and non-twin relatives: an evolutionary perspective

Based on evolutionary reasoning it was hypothesized that: 1. (1) dizygotic (DZ) twins would show greater reduction in grief intensity than monozygotic (MZ) twins for their deceased co-twins,2. (2) female twins would show less reduction in grief intensity than male twins for their deceased co-twins, and3. (3) twins would show less reduction in grief intensity for deceased co-twins than for other deceased relatives. Using a 7-point scale, 175 bereaved twins assessed their grief intensities as recalled 1–2 months after the loss and currently. Decrease in grief intensity was significantly greater for DZ twins than for MZ twins, as expected, although significant gender differences were not found. Participants also evidenced significantly less decrease in grief for deceased co-twins than for other deceased relatives. The implications of these findings for an evolutionary theory of bereavement are discussed.