Lack of association between endoplasmic reticulum stress response genes and suicidal victims

As lithium has been shown to have a protective effect against suicidal behavior, genes on which mood stabilizers act may be involved in biological susceptibility to suicide. A recent study showed that endoplasmic reticulum (ER) stress response was impaired in the bipolar disorders and the impairment was ameliorated by a mood stabilizer, valproate. We hypothesized that an alteration of ER stress response is involved in the biological susceptibility to suicide through genetic polymorphisms, and examined the association of polymorphisms of X-box binding protein 1 (XBP1) and heat shock 70-kDa protein 5 (HSPA5) genes with suicide. We found no significant difference in the distribution of these polymorphisms between the suicide victims and the controls. These results suggest that the polymorphisms examined in this study are not involved in the susceptibility to suicide of the Japanese.