We estimated the risk of suicide associated with SUDs for a general population sample of men and women who receive care in 8 large integrated health care systems spanning a variety of regions across the U.S. Our results suggest that SUDs are associated with significantly increased risk of suicide even after adjusting for other factors that are known to increase risk of suicide, such as psychiatric conditions or physical health comorbidity. We also examined the association of SUDs with risk of suicide for males and females separately. Our results indicate that all categories of SUD are associated with significantly increased risk of suicide for both males and females. Consistent with other studies and known epidemiology [1], we found that in general, men were more likely than women to have died from suicide. For men, the relative risk of suicide associated with SUDs was between 1.8 (tobacco only) and 7.9 (alcohol + drug + tobacco). For women, the relative risk of suicide associated with SUDs was between 2.5 (tobacco only) and 16.7 (alcohol + drug + tobacco). Finally, we found that having multiple SUDs was associated with significantly greater risk of suicide mortality than any of the other SUD categories.

The most comparable study to ours is a recent analysis using data from the VHA [9]. Bohnert and colleagues found increased risk associated with several categories of SUD amongst persons served at VHA facilities. Although the methods are not directly comparable to ours, due to differences in underlying study design, our results are generally in line with Bohnert’s findings that SUDs are consistently associated with an increased risk of suicide mortality. However, in the current study we also find that even after controlling for other important risk factors (e.g., psychiatric diagnoses), all categories of SUD are associated with increased risk of suicide. In contrast, Bohnert et al. find that after adjusting for other risks, increased risk of suicide death is only associated with some kinds of SUD. In addition, Bohnert et al. did not examine diagnosis of multiple types of SUD, while our work suggests that diagnosis of multiple SUDs is associated with increased risk of suicide beyond that associated with any one category of SUD.

Our results suggest that increased screening for suicide risk in persons identified with SUDs may be warranted. This might include screening for suicide risk at entry to substance use treatment programs, or ongoing monitoring for suicide risk during treatment. Although this type of screening or monitoring may be currently happening in some health care systems, more research is needed on systematic programs for monitoring and mitigating risk of suicide in persons with SUD. The small number of studies reported in the literature to date suggest that many addiction providers may not have formal training in suicide risk assessment, or may not consistently incorporate it into care [23]. In addition, health systems might want to consider suicide prevention screening for persons identified with SUDs in other settings such as primary care or emergency settings, where persons may be identified with SUD who are not currently in addiction treatment.

We find that all categories of SUD are associated with significant risk of suicide in both men and women even after controlling for known risk factors, such as psychiatric conditions, or physical health status. We also find that the relative risk associated with SUD is particularly high for women. This result is consistent with observations in the literature suggesting that women may be reluctant to seek care for substance use conditions compared to men, such that the women who are diagnosed have more severe conditions [24]. Our results suggest that health systems pay particular attention to risk of suicide in women with SUD. In addition, further research to explore potential differences in how SUD influences risk of suicide in men and women could help to shape future suicide screening and treatment efforts. Our results are consistent with, but somewhat different than, previous work. Similar to our findings, Bohnert et al. [9] found that after controlling for demographic factors and psychiatric comorbidity, the relative risk of SUD associated with suicide mortality was greater for women compared to men. However, we find a larger difference in relative risk of suicide for women compared with men associated with SUD. Bohnert et al. [9] included only patients served through VHA, and this limits the generalizability of results to a broader population. Our study includes a greater number of women who died of suicide than Bohnert et al. (602 in current study compared to 291 in the VHA study); thus, our study has more power to look at women separately from men.

Many persons with SUD have multiple diagnoses across different categories of SUD (e.g., alcohol, drugs) [25], yet few studies have examined the difference in risk of suicide mortality for single compared to multiple SUD diagnoses. We know of only one study from Mexico that has reported on this issue [26]. Consistent with Ocampo and colleagues, we found that diagnoses of multiple types of SUD are associated with greatly increased risk of suicide mortality for both men and women.

SUDs and some psychiatric conditions often occur together [27]. Yet, little previous research on risk of suicide mortality has been able to control for the effect of SUD in the context of other health conditions such as psychiatric conditions or physical health disorders [2]. The few studies that have addressed this issue suggest that specific psychiatric conditions, such as depression or bipolar disorder, may account for a significant portion of the relationship between SUD and suicide mortality [9, 28]. Our findings also suggest that psychiatric conditions likely play an important role in suicide mortality in those with SUD, but we also find that even after controlling for many types of psychiatric conditions, all categories of SUD remain important risk factors for suicide mortality.

Our results should be considered in light of several limitations. All persons included in our study were covered by private or public health insurance and were members of established integrated health systems. Therefore, the results may not apply to persons without insurance or those served by more fragmented systems. Although the sample of cases is relatively large for a study of suicide death, some of the subgroup analyses include small numbers of subjects, resulting in relatively wide confidence intervals. Because this is an observational study, we cannot rule out confounding due to unmeasured factors. In particular, we were not able to include some demographic variables that may be important moderators of the relationship between SUDs and suicide risk such as race or ethnicity, employment status, or marital status. We included adjustment for known psychiatric conditions, however, it is possible that some patients with SUD may have undiagnosed psychiatric conditions and that could account for some of the increased risk of SUD that we identified. We were not able to examine the risk associated with some specific individual types of drugs (e.g., marijuana), and it is possible that the risks may differ by type of drug. We also did not have measures of the severity of SUD. Those with more severe disorders may be driving the differences in suicide risk that we observe. Information on diagnoses of SUD are dependent on health care providers coding these diagnoses; thus some individuals with SUD may have been missed because health care providers did not recognize the disorder, or chose not to record the diagnosis. Thus, some controls may have undiagnosed SUD and this may make our results somewhat conservative. Although we included health system members from multiple states representing different geographic regions, not all U.S. states or healthcare settings were represented. In contrast to previous work, we did not match on age and gender. We limited matching to location and year, so that future analyses in this line of research could investigate variation in subgroups through analyses using interaction, stratification, and adjustment. In lieu of matching, this study adjusted the analyses for both age and gender. Although we used robust methods for identifying suicide death [29], it is possible that some deaths identified as suicide were accidental overdoses, as this can be difficult to distinguish in persons with some types of SUD [30].

Despite these limitations, our study provides one of the first reports of risk of suicide amongst individuals with SUDs in a general population. All SUD categories studied were associated with increased risk of suicide and our results suggest that health systems could increase screening and monitoring of suicide risk and plan services to help address suicide risk amongst persons with SUD. The focus of this study was examining the risk of suicide for persons with SUD. However, persons who are identified by health systems as at risk for suicide are also more likely at risk for SUD [31], therefore health systems may want to screen persons identified as at risk for suicide for SUD and to offer evidence-based treatment for SUD where warranted. Health systems may want to pay particular attention to how current services address suicide risk for women with SUD. Future research to better understand the significant relative risk of suicide amongst women with SUD could greatly aid health systems and providers to better serve women with SUD.