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Concurrent mental and substance use disorders in Canada

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by Saeeda Khan

Concurrent disorders, also known as dual diagnosis or dual disorder, typically refer to the simultaneous occurrence of a mental and a substance use disorder.^{Note 1Note 2} Individuals with concurrent disorders often experience poorer physical health^{Note 3} and greater psychological distress^{Note 4} than do people with a single disorder. They may also receive less-than-optimal health care.^{Note 5} The complex health care needs of this subpopulation can result in long hospital stays, high readmission rates, and increased health care costs.^{Note 6Note 7Note 8}

The dual nature of concurrent disorders can trigger a self-perpetuating cycle that contributes to poor outcomes, including a high risk of relapse if the disorders are not treated simultaneously.^{Note 6Note 7} Integrating the delivery systems to treat concurrent mental health and substance use problems is a recognized challenge.^{Note 5Note 7Note 8Note 9}

While the disorders that most commonly co-occur are mood/anxiety and substance use disorders,^{Note 2} many other groupings have been examined—for instance, substance use with psychoses or with eating or gambling disorders.^{Note 2} This makes it difficult to trace prevalence rates across time, and can result in underestimation of the overall prevalence of concurrent disorders.^{Note 10}

Much of the literature has relied on older data^{Note 11Note 12} and examined lifetime rather than past 12-month measures, which increases the probability that the disorders were not present at the same time. More recent analyses^{Note 1Note 4Note 13} that focused on past 12-month disorders used the 2002 Canadian Community Health Survey Mental Health and Well-being, which collected information on a selection of mental disorders different from those in the present analysis.

This study is the first to use the 2012 Canadian Community Health Survey–Mental Health to examine the demographic and socioeconomic characteristics, health status and health care service use of people with concurrent disorders, and compare them with people who had a mood/anxiety or a substance use disorder only (see The data). Respondents with concurrent disorders were defined as those who, in the past 12 months, had at least one mood/anxiety disorder and at least one substance use disorder. The mood/anxiety disorders were major depressive episode, bipolar I/bipolar II disorder and generalized anxiety disorder. The substance use disorders were alcohol, cannabis and other drug abuse or dependence. Estimates were calculated for the household population aged 15 to 64 in the 10 provinces.

Prevalence (past 12-month) by disorder type

In 2012, an estimated 6.1% of the Canadian household population aged 15 to 64 had a mood/anxiety disorder in the previous year, and 3.8% had a substance use disorder (Table 1). An additional 1.2% (282,000) experienced concurrent mood/anxiety and substance use disorders, an estimate similar to the 1.7% prevalence of concurrent disorders based on results of the 2002 CCHS Mental Health and Well-being,^{Note 1} which measured a slightly different range of mental illnesses.

The prevalence of concurrent disorders did not vary significantly by sex—1.4% of men and 1.1% of women. However, consistent with the literature,^{Note 1Note 13Note 14} women were more likely than men to have a mood/anxiety disorder (7.8% versus 4.5%), and substance use disorders were more common in men than women (5.8% versus 1.9%).

The prevalence of concurrent disorders and substance use disorders declined with advancing age, whereas the prevalence of mood/anxiety disorders peaked at ages 25 to 44.

Marital and socioeconomic status

People with concurrent disorders were significantly more likely than those with a mood/anxiety disorder to be single, and significantly less likely to be married (Table 2). The high percentage of single people among those with concurrent disorders is partially attributable to their younger age profile: 43% were aged 15 to 24, compared with 20% of people with a mood/anxiety disorder.

The distributions by household education, employment and household income status of individuals with concurrent disorders and of those with a mood/anxiety disorder did not differ significantly. By contrast, compared with people who had a substance use disorder, lower percentages of those with concurrent disorders were employed or in the top two household income adequacy quintiles, and a higher percentage were in the bottom two household income quintiles.

Physical and psychological health

An estimated 29% of people with concurrent disorders reported that they had at least two chronic conditions (Table 3). This was significantly below the percentage among those with a mood/anxiety disorder (39%), but significantly above the estimate for those with a substance use disorder (13%).

Similar percentages of people with concurrent disorders or a mood/anxiety disorder perceived their health to be fair or poor (35% and 37%); the figure among those with a substance use disorder was significantly lower (17%). Mood/Anxiety disorders and substance use disorders have been shown to be bidirectionally associated with chronic conditions.^{Note 15Note 16} The presence of a chronic condition can precipitate a mood/anxiety or a substance use disorder, while some chronic conditions can be triggered by a mood/anxiety disorder or a substance use disorder.^{Note 17Note 18Note 19}

Individuals with concurrent disorders were significantly more likely than those with a substance use disorder to perceive their mental health to be fair or poor (53% versus 9%) and to report high life stress (51% versus 22%). Differences between the perceived mental health and life stress of the concurrent disorders and mood/anxiety disorder groups were not significant.

Fully 91% of those with concurrent disorders reported high psychological distress, significantly above the percentages among those with a mood/anxiety (79%) or a substance use (34%) disorder.

Service use

Individuals with concurrent disorders (76%) were more likely than those with only a mood/anxiety (67%) or substance use disorder (21%) to have received help for their emotions, mental health or substance use in the past 12 months (Table 4). This was generally the case for both formal and informal consultations, except that the percentages of the concurrent disorders and mood/anxiety disorder groups reporting formal sources did not differ significantly.

Despite the high percentages who reported health care consultations, 39% of those with concurrent disorders perceived that they had an unmet or only partially met need for mental health care. This was four times the figure for people with a substance use disorder (10%), but not statistically different from the figure for those with a mood/anxiety disorder (32%). Similarly, an earlier study showed higher odds of unmet needs among people with concurrent disorders, when service use, socio-demographic characteristics, psychological distress, and mental health status were taken into account.^{Note 4}

Multivariate regression

Even with adjustments for the effects of age, sex, marital status, household education, employment status, household income and the number of chronic conditions, the analysis revealed significantly poorer self-perceived mental health and higher psychological distress among individuals with concurrent disorders, compared with those who had only a mood/anxiety disorder or a substance use disorder (Table 5). These results confirm findings from the descriptive analysis (Table 3).

As well, when socio-demographic factors and chronic conditions were taken into account, individuals with concurrent disorders had significantly higher odds of health service use and higher odds of partially met or unmet health care needs than did people with only a mood/anxiety or a substance use disorder. Again, the results confirm findings from the descriptive analysis (Table 4).

Conclusion

In 2012, an estimated 282,000 Canadians aged 15 to 64 (1.2%) had experienced both a mood/anxiety disorder and a substance use disorder in the previous year. The socio-demographic characteristics of this group set them apart from those with only a mood/anxiety disorder or a substance use disorder. As well, compared with the two latter groups, people with concurrent disorders had poorer psychological health, higher health service use, and were more likely to report partially met or unmet needs. These findings suggest that the complexity of concurrent disorders contributes to poorer psychological health status and higher service use, compared with having only a mood/anxiety disorder or a substance use disorder.

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