A Twin Study of Suicide

Abstract

Suicide is a complex problem and a phenomenon of mankind which is obviously influenced by a multitude of ethnological, socio-cultural, psychological and various other factors.That a man takes his own life does not necessarily mean that he was mentally abnormal. On the other hand, it is a well established fact that the frequency of mental illness — affective disorders in particular — is high among suicides, and that one in six patients suffering from manic-depressive psychosis will commit suicide (Sainsbury, 1968). A family history of suicide is not quite uncommon, and beforehand one cannot exclude the possibility that somehow genetic factors may play a part in suicide; but evidence in favour of such an assumption seems to be scanty.A survey of the literature reveals that there have been very few twin studies of suicide, and so far concordance in MZ twins seems to have been reported in three cases only.The first case was observed, already in 1812, by a Dr. Stephens Williams from Massachusetts. He described twin brothers, presumably MZ, who both were captains and had distinguished themselves in the War of Independence. One of the twins settled down in the beautiful state of Vermont, whereas the other remained in Springfield. For several years, they continued to live apart, until, within short interval, they both committed suicide by cutting their throat. Williams points out that the mother and two siblings of the twins had presented symptoms of mental illness, and that, prior to their death, both had been in a state of melancholy, probably an endogenous depression.

Family History of Suicide Among Suicide Victims

“…Nevertheless, the strongest risk factor for suicide in the families was mental disorder, defined by previous psychiatric inpatient care. The strong connection between suicide and mental disorder is well established (1)(2)(3)(4)(5)(6)(7)(8). But still, a family history of suicide was a significant risk factor independent of severe mental disorder.…”

“…Suicide in family members appears to be a predisposing factor for suicide irrespective of psychopathology (6). Genetic transmission has been emphasized (6)(7)(8)(9); however, an environmental effect has also been demonstrated (9). These studies were based on relatively small, selected study groups.…”

Genetic influences on suicide and nonfatal suicidal behavior: Twin study findings

“…Among 149 twin pairs in which at least one twin died by suicide, nine MZ pairs were concordant, yielding a 30% probandwise concordance rate. A study of suicides in the population-based Danish Twin Registry [7] reported four concordant MZ pairs among 19 MZ pairs with at least one affected twin (35%) and no concordant DZ pairs.…”

Genetics of suicide: a systematic review of twin studies

“…This study was based on the national Danish twin register, which included the total twin population born in Denmark 1870-1910 and all same-sex pairs born 1911-1920. There are various supplemental accounts dealing with this sample [75][76][77].…”