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Familial transmission of suicidal ideation and suicide attempts: evidence from a general population sample
Psychiatry Research 126 (2004) 159–165
Familial transmission of suicidal ideation and suicide attempts: evidence from a general population sample Renee D. Goodwina,*, Annette L. Beautraisb, David M. Fergussonc Department of Epidemiology, Mailman School of Public Health, Columbia University, 1051 Riverside Drive, Unit 噛43, New York, NY 10032, USA b Canterbury Suicide Project, Christchurch School of Medicine, Christchurch, New Zealand c Department of Psychological Medicine, Christchurch School of Medicine, Christchurch, New Zealand
a
Received 20 February 2004; received in revised form 22 February 2004; accepted 23 February 2004
Abstract The goals of the study were (1) to determine the association between parental and offspring suicidal ideation and suicide attempts among adult offspring in a general community sample, and (2) to examine the extent to which this association can be explained by mediating processes of mental disorders. Data were drawn from the National Comorbidity Survey (ns8098), a representative household sample of adults aged 15–54 in the United States. The relationships between suicidal ideation and suicide attempts among adult offspring and suicidal ideation and suicide attempt in their parents, compared with those in parents not characterized by suicidal ideation or suicide attempts, were calculated using multiple logistic regression analyses. Analyses were adjusted for differences in sociodemographic characteristics and for mental disorders. Results showed that parental suicidal ideation was associated with a significantly increased likelihood of suicidal ideation wORs1.7 (1.2, 2.5)x and suicide attempt wORs1.4 (0.9, 2.1)x among offspring. Parental suicide attempt was associated with increased odds of suicidal ideation wORs2.0 (1.4, 2.9)x and suicide attempt wORs2.2 (1.4, 3.4)x among offspring. Comorbid mental disorders contributed to the strength of these associations, but with the exception of the link between parental suicidal ideation and offspring suicide attempt, all remained statistically significant even after adjustment. These data provide initial evidence of familial linkages (parent-offspring) of suicidal ideation and behavior among a sample of adults representative of the US population. The data suggest that comorbid mental disorders contribute to these associations but do not completely account for them. The findings are consistent with and extend results from family, clinical, and high-risk studies suggesting that a familial risk of suicidal ideation and suicide behavior occurs in the general population. Implications for prevention and future research are discussed. 䊚 2004 Elsevier Ireland Ltd. All rights reserved.
Keywords: Suicidality; Epidemiology; Depression
*Corresponding author. Tel.: q1-212-305-6707; fax: q1-212-305-9413. E-mail address: [email protected] (R.D. Goodwin). 0165-1781/04/$ - see front matter 䊚 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.psychres.2004.02.010
160
R.D. Goodwin et al. / Psychiatry Research 126 (2004) 159–165
1. Introduction Suicidal ideation and suicide attempts are a major public health problem in the United States and worldwide (World Health Organization, 1990; Cantor and Neulinger, 2000). Suicidal ideation is associated with increased likelihood of mental disorders (e.g. Malone et al., 1995; Gould et al., 1998; Kessler et al., 1999), psychiatric comorbidity (e.g. Kessler et al., 1999; Roy-Byrne et al., 2000), impairment in social and occupational functioning (e.g. Lish et al., 1996; Olfson et al., 1996), and suicide behavior (e.g. Petronis et al., 1990; Gould et al., 1996; Borges et al., 2000). Suicide attempts are the strongest risk factor for suicide completion (Rich et al., 1988; Brent et al., 2002; Nordentoft et al., 2002), and are independently associated with high rates of psychiatric morbidity (e.g. Kessler et al., 1999). A number of studies have reported an association between suicidal behavior (suicidal ideation and suicide attempt) in parents and suicide behavior (suicidal ideation and suicide attempt) in offspring (e.g. Egeland and Sussex, 1985; Beautrais et al., 1996; Brent et al., 2002). Results of several family studies based on probands with a history of suicide attempt in psychiatric treatment settings (e.g. Wender et al., 1986; Brent et al., 1996, 2002; Statham et al., 1998; Cheng et al., 2000) have shown linkages between family histories of suicide and suicide attempt and increased risk of suicide behavior among family members. This relationship has also been documented in population samples (Beautrais et al., 1996; Fergusson et al., 2003). For example, a recent study showed that family histories of suicide and suicide attempt were associated with increased vulnerability to suicide behavior in a community-based sample of young persons in New Zealand (Fergusson et al., 2003). Only two recent ˚ studies (i.e. Qin et al., 2002; Runeson and Asberg, 2003) have shown familial risk of suicide completion in population-based data. Qin et al. (2002) found that family history of completed suicide was a risk factor for suicide, independent of the effect of family history of mental disorders in a population-based study in Denmark. Similarly, Runeson ˚ and Asberg (2003) found evidence of familial clustering of suicide in the general population by
examining rates of suicide in family members of suicide victims and comparison subjects who died of other causes in Sweden. This study found 9.4% of deaths in relatives of suicide victims compared with 4.6% in victims of other death causes. While the existing evidence cumulatively suggests that suicidal behavior has a strong familial risk and may even be genetically transmitted to some extent, several questions remain about the applicability of these findings. Firstly, previous studies have examined the relationship between family history of suicidal ideation and suicide attempt and increased risk of suicide behavior in youth in the community, yet previous studies have not examined whether this relationship is generalizable to adults in the community as well. Secondly, previous studies suggest that family history of suicide attempt and suicide completion is associated with an increased familial risk of suicide behavior. Yet, previous studies have not examined the relationship between family history of suicidal ideation and the risk of suicidal ideation in the community. Finally, there is a need to clarify the extent to which parentyoffspring resemblance in suicidal behavior reflects a specific association in suicide response or a more pervasive association involving mental health problems in general. Against this background, the goal of the current study is to investigate the association between parental suicidal ideation and suicide attempts and suicidal ideation and suicide attempts among offspring in the community. The study addresses three main issues: (1) To what extent are suicidal ideation and suicide attempts in parents associated with suicidal ideation and suicide attempts in offspring among adults in the community? (2) Can associations between parental suicidality and suicidality in offspring be explained by confounding sociodemographic factors? (3) To what extent are the associations between parental suicidality and suicidality in offspring mediated by intervening mental health processes in the offspring? That is, is parental suicidality related to mental health problems in offspring, which are in turn associated with increased risk of suicidality? Based on the previous findings from clinical samples, we hypothesized that parental suicidal ideation and suicide attempt would be associated
R.D. Goodwin et al. / Psychiatry Research 126 (2004) 159–165
with increased suicidal ideation and suicide attempt among adult offspring in the community. We expected that these associations would persist independent of differences in sociodemographic factors and mental disorders. 2. Methods 2.1. Sample The National Comorbidity Survey is based on a national probability sample (ns8098) of individuals aged 15 to 54 in the non-institutionalized population (Kessler et al., 1994, 1995). Field work was carried out between September 1990 and February 1992. There was an 82.4% response rate. The data were weighted for differential probabilities of selection and non-response. A weight was also used to adjust the sample to approximate the cross-classification of the population distribution on a range of sociodemographic characteristics. Weighting and a full description of study methodology are described in detail elsewhere (Kessler et al., 1994, 1995). 2.2. Diagnostic assessment Psychiatric diagnoses were generated from a modified version of the World Health Organization (WHO) Composite International Diagnostic Interview (World Health Organization, 1990), a structured interview designed for use by trained interviewers who are not clinicians. WHO field trials (Wittchen, 1994) and National Comorbidity Survey clinical reappraisal studies (Blazer et al., 1994; Wittchen et al., 1995, 1996) documented acceptable reliability and validity of all the diagnoses. Psychiatric disorders examined here include major depression, generalized anxiety disorder, agoraphobia, simple phobia, social phobia, posttraumatic stress disorder, non-affective psychosis, antisocial personality disorder, conduct disorder, bipolar disorder, dysthymia, mania, alcohol use disorder, and substance use disorder. Written informed consent was obtained from each participant after the survey had been fully explained.
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2.2.1. Assessment of suicidal ideation and suicide behavior All respondents were asked the following questions to evaluate suicidal ideation and history of suicide attempt, respectively, as part of the LifeEvent History section of the NCS interview: ‘Have you ever seriously thought about committing suicide?’ and ‘Have you ever attempted suicide?’ (Kessler et al., 1999). 2.2.2. Assessment of family history of suicidal ideation and suicide behavior The Family History section of the NCS interview survey (part 2) contained a section evaluating, in natural mothers and natural fathers of the respondent, their history of five disorders including major depression. The Family History Research Diagnostic Criteria (Endicott et al., 1978) for ‘depressive disorder’ were used, which included the question: ‘Think of the time when his depression was at its worst. During that time, did your (motheryfather)«Did sheyhe talk about or attempt to harm heryhimself in any way?’ A separate question was asked regarding suicide attempts to all respondents: ‘Did your natural motheryfather ever attempt to commit suicide?’ Separate questions were asked for mother and father. 2.3. Analytic strategy Multiple logistic regression analyses were used to determine the association between parental suicidal ideation and suicidal ideation among offspring by calculating odds ratios with 95% confidence intervals. The same analyses were then repeated for the link between parental and offspring suicide attempt. Analyses were adjusted for differences in sociodemographic factors (age, gender, race, marital status, income, and education), and additionally for depression, dysthymia, bipolar disorder, panic attacks, agoraphobia, generalized anxiety disorder, specific phobia, social phobia, non-affective psychosis, alcohol dependence, and substance use dependence.
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Table 1 Associations (odds ratios, OR) between parental suicidality (ideation, attempts) and suicidality in offspring (ideation, suicide plan, attempts) Offspring suicidality
Males % Ideation % Suicide attempt Females % Ideation % Suicide attempt Total % Ideation % Suicide attempt
Parental suicidality Ideation
Attempt
No
Yes
OR (95% CI)
No
Yes
OR (95% CI)
12.8 (343) 3.4 (92)
33.5 (53) 13.9 (22)
3.8* (2.3, 6.19) 4.4* (2.58, 7.43)
13.1 (357) 3.37 (92)
36.45 (39) 20.56 (22)
5.1* (2.92, 8.74) 6.8* (3.75, 12.38)
19.0 (520) 7.6 (208)
30.6 (92) 14.6 (44)
2.3* (1.62, 3.39) 2.2* (1.5, 3.19)
19.1 (545) 7.54 (215)
35.83 (67) 19.79 (37)
2.6* (1.68, 4.05) 3.4* (2.14, 5.28)
15.9 (863) 5.5 (300)
31.6 (145) 14.4 (66)
2.9* (2.2, 4.0) 3.0* (2.1, 4.1)
16.2 (902) 5.5 (307)
36.1 (106) 20.1 (59)
3.5* (2.4, 5.0) 4.6* (3.1, 6.6)
*P-0.05.
3. Results 3.1. Rates of suicidal ideation and suicide attempt in the NCS The lifetime prevalence of suicidal ideation in the NCS was 13.5% (S.E.s0.6) and that of history of suicide attempt was 4.6% (0.4) (as reported previously in Kessler et al., 1999). 3.2. Association between parental suicidal ideation and suicide attempts and suicidal ideation and suicide attempts in offspring Table 1 shows the associations between suicidal ideation and suicide attempts in parents and suicidal ideation and suicide attempt in offspring. Separate data are shown for males, females, and the total sample. The table shows that in all cases, suicidal tendencies in parents were associated with increased suicidal ideation and suicide attempt in offspring. These associations held for males, females, and the total sample. Logistic models fitted to the data in Table 1 failed to show any
gender by parental suicidal ideation–suicide attempt interactions, suggesting that the effects of parental suicidal ideation and suicide attempt on offspring suicidal ideation and suicide attempt are the same for males and females. For this reason, the data were pooled over gender groups in subsequent analyses. 3.3. Association between parental suicidal ideation and suicide attempts and suicidal ideation and suicide attempts in offspring adjusted for covariates Table 2 shows the associations odds ratios (ORs) between parental suicidal ideationysuicide attempt and offspring suicidal ideationysuicide attempt after adjustment for (a) potentially confounding factors including age, gender, race, marital status, income and education; and (b) potentially intervening mental health variables including depression, dysthymia, bipolar disorder, panic attacks, agoraphobia, generalized anxiety disorder, specific phobia, social phobia, non-affective psychosis, alcohol dependence, substance use
R.D. Goodwin et al. / Psychiatry Research 126 (2004) 159–165 Table 2 Odds ratios (OR) between parental suicidality (ideation, attempts) and suicidality in offspring (ideation, suicide plan, attempts) adjusted for demographic factorsa, and both demographic factors and mental disordersb Offspring suicidality
Parental suicidality Ideation Adj. OR
Ideation
Attempt a
2.7* (2.0,3.7) Suicide attempt 2.7* (1.9,3.8)
Adj. OR
b
1.7* (1.2,2.5) 1.4 (0.9,2.1)
Adj. ORa Adj. ORb 3.2* (2.3,4.6) 4.0* (2.7,5.7)
2.0* (1.4,2.9) 2.2* (1.4,3.4)
*P-0.05. a Demographic factors were age, gender, race, marital status, income, and education. b Mental disorders were depression, dysthymia, bipolar disorder, panic attacks, agoraphobia, generalized anxiety disorder, specific phobia, social phobia, non-affective psychosis, alcohol dependence, and substance use dependence.
dependence. The table shows that adjustment for confounding sociodemographic factors reduced the associations between parent and offspring suicidal ideationysuicide attempt by only a small amount. However, control for intervening mental health factors reduced these associations more substantially. Nonetheless, even after such control, most of the associations between parental SIySA and offspring suicidal ideationysuicide attempt remained statistically significant. 4. Discussion This study confirms the results of previous clinical (e.g. Egeland and Sussex, 1985; Brent et al., 1996, 2002; Cheng et al., 2000) and community-based studies (Beautrais et al., 1996; Fergusson et al., 2003) and suggests increased rates of suicidal ideation and suicide attempt among offspring of parents with suicidal ideation and suicide attempts. These results held for both males and females. There seems to be little doubt on the basis of this evidence that there is a pervasive tendency for suicidal behaviors to run in families. In this article, we have examined two further issues relating to this association. The first concerns the extent to which parent-offspring resemblance in suicidality was reflective of third confounding
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factors that are associated with suicidality in both parent and offspring. Control for a range of factors (i.e. age, gender, race, marital status, income, and education) had only a small effect on these associations, suggesting that it was unlikely (although not impossible) that parent–offspring associations could be explained by third or confounding factors. The analysis was then extended to examine the extent to which parent–child associations could be explained by intervening mental health factors involving the offspring. Specifically, it could be hypothesized that the associations between parental suicidality and suicidality in offspring arise from a causal chain process in which (a) parental suicidal ideation is associated with increased mental health problems in offspring and (b) increased mental health problems are associated with increased risk of suicidal ideation and suicide attempt. This explanation implies that parent suicidality and suicidality in offspring will be uncorrelated when due allowance is made for the effects of mental health variables. Conversely, evidence showing that parental and offspring suicidality are associated after control for mental health factors would suggest a specific association in which suicidality of the parent leads to suicidality in the offspring. The results of the present analysis tended to strongly favor the latter hypothesis. Although control for intervening mental health factors explained some of the association between parental suicidality and suicidality in the offspring, even after control for intervening mental health factors, respondents with a history of parental suicidal ideation had an increased risk of suicidal ideation (but not attempt) whereas those with a history of parental suicide attempt had an increased risk of both suicidal ideation and suicide attempt. These findings suggest a specific relationship in which parent suicidal ideation leads to suicidal ideation in offspring; and suicide attempt in the parent leads to both suicidal ideation and suicide attempt in offspring. Nonetheless, control for mental disorders did reduce the association somewhat, suggesting that some component of parent-offspring resemblance in suicidality may be mediated by intervening mental health factors. Limitations of this study should be considered when interpreting these results. The measurement
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of suicidal thoughts and behavior is limited, due to the use of only one question to assess each. Replication of these findings in future studies with more extensive evaluation of suicide ideation and suicide behavior is needed. As noted above, family-history methods of assessment of suicide behavior in family members could lead to biased estimates. For instance, overreporting is possible among respondents with suicidal behavior or underreporting could occur in the cases where history of parental suicidal behavior may not be known by offspring. Previous family study data suggest a tendency for probands with a specific disorder to overreport this disorder in their firstdegree relatives (Chapman et al., 1994). Yet, it is also plausible to think that offspring are unaware of suicidal ideation in parents in some cases, though it seems less likely that offspring would overreport suicide attempts among parents. References Beautrais, A.L., Joyce, P.R., Mulder, R.T., Fergusson, D.M., Deavoll, B.J., Nightingale, S.K., 1996. Prevalence and comorbidity of mental disorders in persons making serious suicide attempts: a case-control study. American Journal of Psychiatry 153, 1009–1014. Blazer, D.G., Kessler, R.C., McGonagle, K.A., Swartz, M.S., 1994. The prevalence and distribution of major depression in a national community sample: the National Comorbidity Survey. American Journal of Psychiatry 151, 979–986. Borges, G., Walters, E.E., Kessler, R.C., 2000. Associations of substance use, abuse, and dependence with subsequent suicidal behavior. American Journal of Epidemiology 151, 781–789. Brent, D.A., Bridge, J., Johnson, B.A., Connolly, J., 1996. Suicidal behavior runs in families. A controlled family study of adolescent suicide victims. Archives of General Psychiatry 53, 1145–1152. Brent, D.A., Oquendo, M., Birmaher, B., Greenhill, L., Kolko, D., Stanley, B., Zelazny, J., Brodsky, B., Bridge, J., Ellis, S., Salazar, J.O., Mann, J.J., 2002. Familial pathways to early-onset suicide attempt: risk for suicidal behavior in offspring of mood-disordered suicide attempters. Archives of General Psychiatry 59, 801–807. Cantor, C., Neulinger, K., 2000. The epidemiology of suicide and attempted suicide among young Australians. Australian and New Zealand Journal of Psychiatry 34, 370–387. Chapman, T.F., Mannuzza, S., Klein, D.F., Fyer, A.J., 1994. Effects of informant mental disorder on psychiatric family history data. American Journal of Psychiatry 151, 574–579. Cheng, A.T., Chen, T.H., Chen, C.C., Jenkins, R., 2000. Psychosocial and psychiatric risk factors for suicide. Case-
control psychological autopsy study. British Journal of Psychiatry 177, 360–365. Egeland, J.A., Sussex, J.N., 1985. Suicide and family loading for affective disorders. Journal of the American Medical Association 254, 915–918. Endicott, J., Andreasen, N., Spitzer, R.L., 1978. Family History Research Diagnostic Criteria. Biometrics Research Department, New York State Psychiatric Institute, New York. Fergusson, D.M., Beautrais, A.L., Horwood, L.J., 2003. Vulnerability and resiliency to suicidal behaviours in young people. Psychological Medicine 33, 61–73. Gould, M.S., Fisher, P., Parides, M., Flory, M., Shaffer, D., 1996. Psychosocial risk factors of child and adolescent completed suicide. Archives of General Psychiatry 53, 1155–1162. Gould, M.S., King, R., Greenwald, S., Fisher, P., SchwabStone, M., Kramer, R., Flisher, A.J., Goodman, S., Canino, G., Shaffer, D., 1998. Psychopathology associated with suicidal ideation and attempts among children and adolescents. Journal of the American Academy of Child and Adolescent Psychiatry 37, 915–923. Kessler, R.C., Borges, G., Walters, E.E., 1999. Prevalence and risk factors for lifetime suicide attempts in the National Comorbidity Survey. Archives of General Psychiatry 56, 617–626. Kessler, R.C., Little, R.J., Groves, R.M., 1995. Advances in strategies for minimizing and adjusting for survey nonresponse. Epidemiology Review 17, 192–204. Kessler, R.C., McGonagle, K.A., Zhao, S., Nelson, C.B., Hughes, M., Eshleman, S., Wittchen, H.U., Kendler, K.S., 1994. Lifetime and 12-month prevalence of DSM-III-R psychiatric disorders in the United States. Results from the National Comorbidity Survey. Archives of General Psychiatry 51, 8–19. Lish, J.D., Zimmerman, M., Farber, N.J., Lush, D.T., Kuzma, M.A., Plescia, G., 1996. Suicide screening in a primary care setting at a Veterans Affairs Medical Center. Psychosomatics 37, 413–424. Malone, K.M., Haas, G.L., Sweeney, J.A., Mann, J.J., 1995. Major depression and the risk of attempted suicide. Journal of Affective Disorders 34, 173–185. Nordentoft, M., Jeppesen, P., Abel, M., Kassow, P., Petersen, L., Thorup, A., Krarup, G., Hemmingsen, R., Jorgensen, P., 2002. OPUS study: suicidal behaviour, suicidal ideation and hopelessness among patients with first-episode psychosis. One-year follow-up of a randomised controlled trial. British Journal of Psychiatry Supplement 43, 98–106. Olfson, M., Weissman, M.M., Leon, A.C., Sheehan, D.V., Farber, L., 1996. Suicidal ideation in primary care. Journal of General Internal Medicine 11, 447–453. Petronis, K.R., Samuels, J.F., Moscicki, E.K., Anthony, J.C., 1990. An epidemiologic investigation of potential risk factors for suicide attempts. Social Psychiatry and Psychiatric Epidemiology 25, 193–199. Qin, P., Agerbo, E., Mortensen, P.B., 2002. Suicide risk in relation to family history of completed suicide and psychi-
R.D. Goodwin et al. / Psychiatry Research 126 (2004) 159–165 atric disorders: a nested case-control study based on longitudinal registers. Lancet 360, 1126–1130. Rich, C.L., Fowler, R.C., Fogarty, L.A., Young, D., 1988. San Diego Suicide Study. III. Relationships between diagnoses and stressors. Archives of General Psychiatry 45, 589–592. Roy-Byrne, P.P., Stang, P., Wittchen, H.U., Ustun, B., Walters, E.E., Kessler, R.C., 2000. Lifetime panic-depression comorbidity in the National Comorbidity Survey. Association with symptoms, impairment, course and help-seeking. British Journal of Psychiatry 176, 229–235. ˚ Runeson, B., Asberg, M., 2003. Family history of suicide among suicide victims. American Journal of Psychiatry 160, 1525–1526. Statham, D.J., Heath, A.C., Madden, P.A., Bucholz, K.K., Bierut, L., Dinwiddie, S.H., Slutske, W.S., Dunne, M.P., Martin, N.G., 1998. Suicidal behaviour: an epidemiological and genetic study. Psychological Medicine 28, 839–855.
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Wender, P.H., Kety, S.S., Rosenthal, D., Schulsinger, F., Ortmann, J., Lunde, I., 1986. Psychiatric disorders in the biological and adoptive families of adopted individuals with affective disorders. Archives of General Psychiatry 43, 923–929. Wittchen, H.U., 1994. Reliability and validity studies of the WHO Composite International Diagnostic Interview (CIDI): a critical review. Journal of Psychiatric Research 28, 57–84. Wittchen, H.U., Kessler, R.C., Zhao, S., Abelson, J., 1995. Reliability and clinical validity of UM-CIDI DSM-III-R generalized anxiety disorder. Journal of Psychiatric Research 29, 95–110. Wittchen, H.U., Zhao, S., Abelson, J.M., Abelson, J.L., Kessler, R.C., 1996. Reliability and procedural validity of UMCIDI DSM-III-R phobic disorders. Psychological Medicine 26, 1169–1177. World Health Organization, 1990. World Health Organization: Composite International Diagnostic Interview (CIDI), version 1.0. Author, Geneva, Switzerland.
Familial transmission of suicidal ideation and suicide attempts: evidence from a general population sample Renee D. Goodwina,*, Annette L. Beautraisb, David M. Fergussonc Department of Epidemiology, Mailman School of Public Health, Columbia University, 1051 Riverside Drive, Unit 噛43, New York, NY 10032, USA b Canterbury Suicide Project, Christchurch School of Medicine, Christchurch, New Zealand c Department of Psychological Medicine, Christchurch School of Medicine, Christchurch, New Zealand
a
Received 20 February 2004; received in revised form 22 February 2004; accepted 23 February 2004
Abstract The goals of the study were (1) to determine the association between parental and offspring suicidal ideation and suicide attempts among adult offspring in a general community sample, and (2) to examine the extent to which this association can be explained by mediating processes of mental disorders. Data were drawn from the National Comorbidity Survey (ns8098), a representative household sample of adults aged 15–54 in the United States. The relationships between suicidal ideation and suicide attempts among adult offspring and suicidal ideation and suicide attempt in their parents, compared with those in parents not characterized by suicidal ideation or suicide attempts, were calculated using multiple logistic regression analyses. Analyses were adjusted for differences in sociodemographic characteristics and for mental disorders. Results showed that parental suicidal ideation was associated with a significantly increased likelihood of suicidal ideation wORs1.7 (1.2, 2.5)x and suicide attempt wORs1.4 (0.9, 2.1)x among offspring. Parental suicide attempt was associated with increased odds of suicidal ideation wORs2.0 (1.4, 2.9)x and suicide attempt wORs2.2 (1.4, 3.4)x among offspring. Comorbid mental disorders contributed to the strength of these associations, but with the exception of the link between parental suicidal ideation and offspring suicide attempt, all remained statistically significant even after adjustment. These data provide initial evidence of familial linkages (parent-offspring) of suicidal ideation and behavior among a sample of adults representative of the US population. The data suggest that comorbid mental disorders contribute to these associations but do not completely account for them. The findings are consistent with and extend results from family, clinical, and high-risk studies suggesting that a familial risk of suicidal ideation and suicide behavior occurs in the general population. Implications for prevention and future research are discussed. 䊚 2004 Elsevier Ireland Ltd. All rights reserved.
Keywords: Suicidality; Epidemiology; Depression
*Corresponding author. Tel.: q1-212-305-6707; fax: q1-212-305-9413. E-mail address: [email protected] (R.D. Goodwin). 0165-1781/04/$ - see front matter 䊚 2004 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.psychres.2004.02.010
160
R.D. Goodwin et al. / Psychiatry Research 126 (2004) 159–165
1. Introduction Suicidal ideation and suicide attempts are a major public health problem in the United States and worldwide (World Health Organization, 1990; Cantor and Neulinger, 2000). Suicidal ideation is associated with increased likelihood of mental disorders (e.g. Malone et al., 1995; Gould et al., 1998; Kessler et al., 1999), psychiatric comorbidity (e.g. Kessler et al., 1999; Roy-Byrne et al., 2000), impairment in social and occupational functioning (e.g. Lish et al., 1996; Olfson et al., 1996), and suicide behavior (e.g. Petronis et al., 1990; Gould et al., 1996; Borges et al., 2000). Suicide attempts are the strongest risk factor for suicide completion (Rich et al., 1988; Brent et al., 2002; Nordentoft et al., 2002), and are independently associated with high rates of psychiatric morbidity (e.g. Kessler et al., 1999). A number of studies have reported an association between suicidal behavior (suicidal ideation and suicide attempt) in parents and suicide behavior (suicidal ideation and suicide attempt) in offspring (e.g. Egeland and Sussex, 1985; Beautrais et al., 1996; Brent et al., 2002). Results of several family studies based on probands with a history of suicide attempt in psychiatric treatment settings (e.g. Wender et al., 1986; Brent et al., 1996, 2002; Statham et al., 1998; Cheng et al., 2000) have shown linkages between family histories of suicide and suicide attempt and increased risk of suicide behavior among family members. This relationship has also been documented in population samples (Beautrais et al., 1996; Fergusson et al., 2003). For example, a recent study showed that family histories of suicide and suicide attempt were associated with increased vulnerability to suicide behavior in a community-based sample of young persons in New Zealand (Fergusson et al., 2003). Only two recent ˚ studies (i.e. Qin et al., 2002; Runeson and Asberg, 2003) have shown familial risk of suicide completion in population-based data. Qin et al. (2002) found that family history of completed suicide was a risk factor for suicide, independent of the effect of family history of mental disorders in a population-based study in Denmark. Similarly, Runeson ˚ and Asberg (2003) found evidence of familial clustering of suicide in the general population by
examining rates of suicide in family members of suicide victims and comparison subjects who died of other causes in Sweden. This study found 9.4% of deaths in relatives of suicide victims compared with 4.6% in victims of other death causes. While the existing evidence cumulatively suggests that suicidal behavior has a strong familial risk and may even be genetically transmitted to some extent, several questions remain about the applicability of these findings. Firstly, previous studies have examined the relationship between family history of suicidal ideation and suicide attempt and increased risk of suicide behavior in youth in the community, yet previous studies have not examined whether this relationship is generalizable to adults in the community as well. Secondly, previous studies suggest that family history of suicide attempt and suicide completion is associated with an increased familial risk of suicide behavior. Yet, previous studies have not examined the relationship between family history of suicidal ideation and the risk of suicidal ideation in the community. Finally, there is a need to clarify the extent to which parentyoffspring resemblance in suicidal behavior reflects a specific association in suicide response or a more pervasive association involving mental health problems in general. Against this background, the goal of the current study is to investigate the association between parental suicidal ideation and suicide attempts and suicidal ideation and suicide attempts among offspring in the community. The study addresses three main issues: (1) To what extent are suicidal ideation and suicide attempts in parents associated with suicidal ideation and suicide attempts in offspring among adults in the community? (2) Can associations between parental suicidality and suicidality in offspring be explained by confounding sociodemographic factors? (3) To what extent are the associations between parental suicidality and suicidality in offspring mediated by intervening mental health processes in the offspring? That is, is parental suicidality related to mental health problems in offspring, which are in turn associated with increased risk of suicidality? Based on the previous findings from clinical samples, we hypothesized that parental suicidal ideation and suicide attempt would be associated
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with increased suicidal ideation and suicide attempt among adult offspring in the community. We expected that these associations would persist independent of differences in sociodemographic factors and mental disorders. 2. Methods 2.1. Sample The National Comorbidity Survey is based on a national probability sample (ns8098) of individuals aged 15 to 54 in the non-institutionalized population (Kessler et al., 1994, 1995). Field work was carried out between September 1990 and February 1992. There was an 82.4% response rate. The data were weighted for differential probabilities of selection and non-response. A weight was also used to adjust the sample to approximate the cross-classification of the population distribution on a range of sociodemographic characteristics. Weighting and a full description of study methodology are described in detail elsewhere (Kessler et al., 1994, 1995). 2.2. Diagnostic assessment Psychiatric diagnoses were generated from a modified version of the World Health Organization (WHO) Composite International Diagnostic Interview (World Health Organization, 1990), a structured interview designed for use by trained interviewers who are not clinicians. WHO field trials (Wittchen, 1994) and National Comorbidity Survey clinical reappraisal studies (Blazer et al., 1994; Wittchen et al., 1995, 1996) documented acceptable reliability and validity of all the diagnoses. Psychiatric disorders examined here include major depression, generalized anxiety disorder, agoraphobia, simple phobia, social phobia, posttraumatic stress disorder, non-affective psychosis, antisocial personality disorder, conduct disorder, bipolar disorder, dysthymia, mania, alcohol use disorder, and substance use disorder. Written informed consent was obtained from each participant after the survey had been fully explained.
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2.2.1. Assessment of suicidal ideation and suicide behavior All respondents were asked the following questions to evaluate suicidal ideation and history of suicide attempt, respectively, as part of the LifeEvent History section of the NCS interview: ‘Have you ever seriously thought about committing suicide?’ and ‘Have you ever attempted suicide?’ (Kessler et al., 1999). 2.2.2. Assessment of family history of suicidal ideation and suicide behavior The Family History section of the NCS interview survey (part 2) contained a section evaluating, in natural mothers and natural fathers of the respondent, their history of five disorders including major depression. The Family History Research Diagnostic Criteria (Endicott et al., 1978) for ‘depressive disorder’ were used, which included the question: ‘Think of the time when his depression was at its worst. During that time, did your (motheryfather)«Did sheyhe talk about or attempt to harm heryhimself in any way?’ A separate question was asked regarding suicide attempts to all respondents: ‘Did your natural motheryfather ever attempt to commit suicide?’ Separate questions were asked for mother and father. 2.3. Analytic strategy Multiple logistic regression analyses were used to determine the association between parental suicidal ideation and suicidal ideation among offspring by calculating odds ratios with 95% confidence intervals. The same analyses were then repeated for the link between parental and offspring suicide attempt. Analyses were adjusted for differences in sociodemographic factors (age, gender, race, marital status, income, and education), and additionally for depression, dysthymia, bipolar disorder, panic attacks, agoraphobia, generalized anxiety disorder, specific phobia, social phobia, non-affective psychosis, alcohol dependence, and substance use dependence.
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Table 1 Associations (odds ratios, OR) between parental suicidality (ideation, attempts) and suicidality in offspring (ideation, suicide plan, attempts) Offspring suicidality
Males % Ideation % Suicide attempt Females % Ideation % Suicide attempt Total % Ideation % Suicide attempt
Parental suicidality Ideation
Attempt
No
Yes
OR (95% CI)
No
Yes
OR (95% CI)
12.8 (343) 3.4 (92)
33.5 (53) 13.9 (22)
3.8* (2.3, 6.19) 4.4* (2.58, 7.43)
13.1 (357) 3.37 (92)
36.45 (39) 20.56 (22)
5.1* (2.92, 8.74) 6.8* (3.75, 12.38)
19.0 (520) 7.6 (208)
30.6 (92) 14.6 (44)
2.3* (1.62, 3.39) 2.2* (1.5, 3.19)
19.1 (545) 7.54 (215)
35.83 (67) 19.79 (37)
2.6* (1.68, 4.05) 3.4* (2.14, 5.28)
15.9 (863) 5.5 (300)
31.6 (145) 14.4 (66)
2.9* (2.2, 4.0) 3.0* (2.1, 4.1)
16.2 (902) 5.5 (307)
36.1 (106) 20.1 (59)
3.5* (2.4, 5.0) 4.6* (3.1, 6.6)
*P-0.05.
3. Results 3.1. Rates of suicidal ideation and suicide attempt in the NCS The lifetime prevalence of suicidal ideation in the NCS was 13.5% (S.E.s0.6) and that of history of suicide attempt was 4.6% (0.4) (as reported previously in Kessler et al., 1999). 3.2. Association between parental suicidal ideation and suicide attempts and suicidal ideation and suicide attempts in offspring Table 1 shows the associations between suicidal ideation and suicide attempts in parents and suicidal ideation and suicide attempt in offspring. Separate data are shown for males, females, and the total sample. The table shows that in all cases, suicidal tendencies in parents were associated with increased suicidal ideation and suicide attempt in offspring. These associations held for males, females, and the total sample. Logistic models fitted to the data in Table 1 failed to show any
gender by parental suicidal ideation–suicide attempt interactions, suggesting that the effects of parental suicidal ideation and suicide attempt on offspring suicidal ideation and suicide attempt are the same for males and females. For this reason, the data were pooled over gender groups in subsequent analyses. 3.3. Association between parental suicidal ideation and suicide attempts and suicidal ideation and suicide attempts in offspring adjusted for covariates Table 2 shows the associations odds ratios (ORs) between parental suicidal ideationysuicide attempt and offspring suicidal ideationysuicide attempt after adjustment for (a) potentially confounding factors including age, gender, race, marital status, income and education; and (b) potentially intervening mental health variables including depression, dysthymia, bipolar disorder, panic attacks, agoraphobia, generalized anxiety disorder, specific phobia, social phobia, non-affective psychosis, alcohol dependence, substance use
R.D. Goodwin et al. / Psychiatry Research 126 (2004) 159–165 Table 2 Odds ratios (OR) between parental suicidality (ideation, attempts) and suicidality in offspring (ideation, suicide plan, attempts) adjusted for demographic factorsa, and both demographic factors and mental disordersb Offspring suicidality
Parental suicidality Ideation Adj. OR
Ideation
Attempt a
2.7* (2.0,3.7) Suicide attempt 2.7* (1.9,3.8)
Adj. OR
b
1.7* (1.2,2.5) 1.4 (0.9,2.1)
Adj. ORa Adj. ORb 3.2* (2.3,4.6) 4.0* (2.7,5.7)
2.0* (1.4,2.9) 2.2* (1.4,3.4)
*P-0.05. a Demographic factors were age, gender, race, marital status, income, and education. b Mental disorders were depression, dysthymia, bipolar disorder, panic attacks, agoraphobia, generalized anxiety disorder, specific phobia, social phobia, non-affective psychosis, alcohol dependence, and substance use dependence.
dependence. The table shows that adjustment for confounding sociodemographic factors reduced the associations between parent and offspring suicidal ideationysuicide attempt by only a small amount. However, control for intervening mental health factors reduced these associations more substantially. Nonetheless, even after such control, most of the associations between parental SIySA and offspring suicidal ideationysuicide attempt remained statistically significant. 4. Discussion This study confirms the results of previous clinical (e.g. Egeland and Sussex, 1985; Brent et al., 1996, 2002; Cheng et al., 2000) and community-based studies (Beautrais et al., 1996; Fergusson et al., 2003) and suggests increased rates of suicidal ideation and suicide attempt among offspring of parents with suicidal ideation and suicide attempts. These results held for both males and females. There seems to be little doubt on the basis of this evidence that there is a pervasive tendency for suicidal behaviors to run in families. In this article, we have examined two further issues relating to this association. The first concerns the extent to which parent-offspring resemblance in suicidality was reflective of third confounding
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factors that are associated with suicidality in both parent and offspring. Control for a range of factors (i.e. age, gender, race, marital status, income, and education) had only a small effect on these associations, suggesting that it was unlikely (although not impossible) that parent–offspring associations could be explained by third or confounding factors. The analysis was then extended to examine the extent to which parent–child associations could be explained by intervening mental health factors involving the offspring. Specifically, it could be hypothesized that the associations between parental suicidality and suicidality in offspring arise from a causal chain process in which (a) parental suicidal ideation is associated with increased mental health problems in offspring and (b) increased mental health problems are associated with increased risk of suicidal ideation and suicide attempt. This explanation implies that parent suicidality and suicidality in offspring will be uncorrelated when due allowance is made for the effects of mental health variables. Conversely, evidence showing that parental and offspring suicidality are associated after control for mental health factors would suggest a specific association in which suicidality of the parent leads to suicidality in the offspring. The results of the present analysis tended to strongly favor the latter hypothesis. Although control for intervening mental health factors explained some of the association between parental suicidality and suicidality in the offspring, even after control for intervening mental health factors, respondents with a history of parental suicidal ideation had an increased risk of suicidal ideation (but not attempt) whereas those with a history of parental suicide attempt had an increased risk of both suicidal ideation and suicide attempt. These findings suggest a specific relationship in which parent suicidal ideation leads to suicidal ideation in offspring; and suicide attempt in the parent leads to both suicidal ideation and suicide attempt in offspring. Nonetheless, control for mental disorders did reduce the association somewhat, suggesting that some component of parent-offspring resemblance in suicidality may be mediated by intervening mental health factors. Limitations of this study should be considered when interpreting these results. The measurement
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