Discussion

Current study showed that multiplicative effects of mental disorders on suicidal ideation among Black adults depend on ethnicity. Depression has multiplicative effects with drug abuse and anxiety among African Americans, while drug abuse and anxiety interacted among Caribbean Blacks. 

Assari and colleagues have shown that number of psychiatric disorders has a dose-dependent effect on the first age of development of suicidal ideation among Black adults in the US (12). The study showed that among Blacks, suicidal ideation was found to start at a lower age among Blacks with two or more mental disorders, compared to those with one disorder (12). In another study by Assari, number of psychiatric disorders was an independent risk factor for odds of suicidal ideation, an effect which was independent of ethnicity and gender (14).

Although we know that suicide rates vary among the ethnic groups (44-46), very few studies have  explored  how risk factors of suicide among

Blacks vary based on ethnicity (12-14,42,43). Given that the foreign-born share of the Black American population rose from 1% to 8% between 1960 and 2005 and immigration contributed 20% of the growth of the US black population between 2000 and 2006 (47), it is important to examine the impact of ethnicity on the patterns of suicidal behavior among black Americans if we are to develop effective intervention strategies.

Nationally representative studies have suggested that risk of suicidal behaviors among Blacks depend on ethnicity (15,24). Among adults, 7.5% of Caribbean black men reported lifetime suicide attempt, while the rate was 4.1% among African American men (15). Joe and colleagues have found that Blacks with mental disorders were eight times more likely to attempt to suicide than those without psychiatric disorders (42). Joe and colleagues have shown that African Americans are five times more likely to attempt to suicide compared to their Caribbean Blacks counterparts (45,46). In a study by Assari and colleagues, additive effects of depression, anxiety, posttraumatic stress disorder, drug abuse and alcohol abuse increased the risk of suicidality among Black adults (13). No previous studies had tested the multiplicative effects of mental disorders on suicidality among ethnic groups of Blacks.

We found that ethnicity alters multiplicative effects of psychiatric disorders on suicidal thoughts among Blacks. In a study by Assari and colleagues (13), Caribbean Blacks and African Americans differed in the additive effects of mental disorders on risk of suicidal behaviors. While among African Americans, depression, anxiety, posttraumatic stress disorder and alcohol abuse were associated with the risk of suicidal thoughts, only depression and drug abuse predicted risk of suicidal thoughts for Caribbean Blacks (13).

While in our study effects of multiple psychiatric disorders among ethnic groups of Blacks were synergistic (27), previous studies have reported “sub-additive effects” among other ethnic groups such as Whites (16). Such “sub-additive effects” have been attributed to redundancy in risk for suicide with different psychiatric disorders, as many mental disorders overlap in etiology and phenotype (16-18). For Blacks, however, mental disorders are more chronic and disabling (40), thus they may show synergistic effects (15).

It has been shown that psychiatric disorders have does effects on suicidal ideation (14,41,48,49). However, ethnic differences in the multiplicative effects of anxiety, depression and drug abuse on suicidality of among Blacks are still unknown. The current study extends the literature and suggests that pattern of comorbidity of anxiety, depression, and drug abuse has implication for suicidal ideation, and such effect depends on ethnicity.

The results are very important because mental disorders are the strongest risk factors of suicide in countries such as US (50-53). Up to 98% of people who commit suicide meet criteria for at least one mental disorder. From various psychiatric disorders that increase risk of suicide, depression and drug use account for 30% and 18% of cases of suicides, proportions that are higher than other conditions (54,55). Unique contribution of this study is showing that among ethnic groups of Blacks, the effect of depression, anxiety, and drug use on suicide depend on presence of other mental conditions.

It is not known what causes ethnic differences regarding the effect of psychiatric disorders on suicide. Ethnic differences may be due to the variations in culture, values, socio-historical experiences, socioeconomics, support system, or access to care, that all potentially influence distribution of suicide and suicidal ideation (48). One study has suggested that psychiatric conditions may differently influence hopelessness (56), which is a main predictor of suicide (57).

In a study, Assari and colleagues (13) argued that screening of anxiety and drug abuse may be more important for suicide prevention among African Americans and Caribbean Blacks, respectively. This is in line with a study that has shown anxiety and depression differently influence self-rated mental health of African Americans and Caribbean Blacks (18). Based on the results of current study, suicide prevention programs among Blacks may benefit from tailoring based on ethnicity. Screening for comorbid psychiatric disorders among Blacks who have suicidal ideation may be different for African Americans and Caribbean Blacks. In the presence of drug abuse, comorbid depression among African Americans and comorbid anxiety among Caribbean Blacks may be more important for detection of suicide. So, ethnicity should inform design and implementation of suicide programs (49).

This study had at least four limitations. First, validity of single item measures of suicidal ideation is not known. Validity of such measures may also depend on ethnicity. Participants with high level of stigma may underreport suicidal thoughts, so the outcome may have different misclassification bias based on ethnicity. Second, cross-ethnic comparability of diagnoses of psychiatric disorders such as anxiety, depression and drug using the Composite International Diagnostic Interview is unknown (41). Third, due to using a cross-sectional design, we cannot interpret the associations to be causative. There is still a need for additional research on the complex associations between race, ethnicity, culture, social class, mental disorders, and suicide. Research should explore if culture explains ethnic-specific interactions between psychiatric disorders on suicidal ideation.

Although our findings showed ethnic–specific multiplicative effects of mental disorders on suicidality of Blacks in the United States, a large number of individuals with suicidal behaviors may only have one psychiatric disorder. Thus, our findings should not undermine importance of suicide screening and prevention for individuals with a single psychiatric disorder. However, suicide risk is greatest among Blacks who meet criteria for more than one psychiatric disorder. We also suggest closer suicide monitoring of Blacks who endorse criteria for multiple mental disorders.

Conclusion

Multiplicative effects of depression, anxiety, and drug abuse on suicidal ideation of Blacks may depend on ethnicity.

Acknowledgments

SA is funded by the Heinz C. Prechter Bipolar Research Fund and the Richard Tam Foundation at the University of Michigan Depression Center.

Conflict of Interest

Authors have no conflict of interest.

Funding

The National Survey of American Life (NSAL) is funded by the National Institute of Mental Health (NIMH; U01-MH57716) with supplemental support from the Office of Behavioral and Social Science Research (OBSSR) and the National Institute on Drug Abuse (NIDA) at the National Institutes of Health (NIH) and the University of Michigan.

Authors Contributions

SA was responsible for the design, analysis of the data, drafting the manuscript.

Disclosure

This paper is an extension of paper “Synergistic Effects of Lifetime Psychiatric Disorders on Suicidal Ideation among Blacks in the USA”. ⁽²⁷⁾ As this is a secondary analysis of a national survey, some similarities in the Methods section of the paper. The reason is that more than 300 peer review papers have been published from this survey. Public data was downloaded from The Interuniversity Consortium for Political and Social Research (ICPSR), Institute for Social Research (ISR), University of Michigan.

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