Importance: Clarification of the joint influence of familial patterns of suicide attempts and comorbid mental disorders can enhance the understanding and prevention of suicide attempts.
Objective: To investigate the familial patterns of suicide attempts and comorbid mental disorders and their associations in a 2-site family study of mood and anxiety disorders.
Design, setting, and participants: Data were obtained from 2 parallel community-based family studies conducted in the United States (National Institute of Mental Health [NIMH] study) and in Lausanne, Switzerland (PsyCoLaus study), on the comorbidity of mood and anxiety disorders. The study sample comprised 1119 adult probands and 5355 first-degree relatives. Data were collected and analyzed from October 2004 to December 2016.
Main outcomes and measures: Lifetime suicide attempt and mental disorders in first-degree relatives, obtained through direct interviews or family history reports.
Results: The study included 1119 adult probands (675 female [60.3%] and a mean [SD] age of 50 [12.0] years) and 5355 first-degree relatives (2752 female [51.4%] and a mean [SD] age of 52 [1.5] years). Of these participants, 90 (8.0%) of 1119 probands and 199 (3.7%) of 5355 relatives had a lifetime history of suicide attempt. Those with such a history had higher rates of all mental disorders, a greater number of disorders, and statistically significantly poorer current and lifetime global functioning. After adjustment for age and sex, a statistically significant association between suicide attempts in probands and in relatives was found at the NIMH site (OR, 2.6; 95% CI, 1.5-4.7), at the Lausanne site (OR, 3.1; 95% CI, 1.6-6.0), and in the combined data (OR, 2.9; 95% CI, 1.9-4.5). All mood disorder subtypes and substance use disorders were statistically significantly associated with suicide attempts. The familial association between lifetime suicide attempts in probands and relatives was not statistically significant for the combined sample (OR, 1.6; 95% CI, 1.0-2.7) after adjustment for comorbid conditions in probands and relatives. Social anxiety disorder in probands was associated with suicide attempts in relatives (OR, 2.4; 95% CI, 1.7-3.5) after controlling for comorbid mood, anxiety, and substance use disorders.
Conclusions and relevance: Familiality of suicide attempts appears to be explained by a history of mental disorders among those with suicide attempts; the novel finding of a common familial diathesis for suicide attempts and social anxiety, particularly in combination with mood disorders, has heuristic value for future research and may be a risk marker that can inform prevention efforts.