The Relationship Between Substance Use and Mental Health Problems

Having a mental health problem increases the risk of having a substance use problem, just as having a substance use problem increases the risk of having a mental health problem (Health Canada, 2002). As well, substance use can cause behaviours that mimic symptoms of mental health problems. These substance-induced problems improve as substance use is decreased or stopped.

Factors that affect the relationship

The nature of the relationship between substance use and mental health has been a topic of concern among clients, families and professionals for years. Are the substance use behaviours causing psychiatric symptoms? Are the mental health issues leading people to use substances to get relief from their troubled mental states? Unfortunately, the relationship between co-occurring mental health and substance use problems is usually much more complicated than simple cause-and-effect:

• There can be, for example, predisposing factors that affect vulnerability to certain problems.
• There can be precipitating factors that relate to the initiation or onset of problems.
• And there are usually perpetuating factors that shape the way problems continue.

Even when one problem was clearly present before the other, the problems may interact, and the relationship between them may change over time.

Interaction models

Degenhardt et al. (2003) suggest four types of models to explain concurrent disorders:

• Common factor models explain that the same set of factors can contribute to increased risk both of substance use and mental health problems. These risk factors may be biological (genetic or disturbances in neurotransmitter function), related to temperament, social or environmental.
• Secondary substance use models hold that mental health problems increase the chances of developing a substance use disorder. The self-medication hypothesis, which holds that people use substances to relieve symptoms of mental health problems, is one well-known example of a secondary substance use model. This explanation appears to be more relevant when considering problems related to mood, anxiety and impulsivity than to psychosis. For example, there is evidence that people use alcohol to help them cope with anxiety problems (Thomas et al., 2003). Other theories include alleviation of dysphoria hypothesis; multiple risk factor model; supersensitivity model; and iatrogenic (problems caused by treatment) vulnerability.
• In secondary mental health models, substance use may precipitate mental health problems in people who would not otherwise have developed them. For example, cannabis use may precipitate psychotic symptoms in people who are already vulnerable (Hall & Degenhardt, 2000).
• Bidirectional models take the view that one problem increases the person’s vulnerability to developing problems in the other area. For example, a person who has severe substance use problems may have problems holding a job. This in turn may increase the person’s risk of developing depression.

It is also possible—if not common—to find co-occurring disorders that are largely independent of one another. That is, they are both present, but their interactive effect is weak.

Determining the functional relationship between substance use behaviour and mental health problems often shapes the counsellor’s expectation (e.g., of what will happen if the client stops substance use). If the client is experiencing problems directly linked to substance use, stopping or reducing use is likely to lead to improvement in mental health symptoms. On the other hand, if the client is using substances to get relief from distressing mental states or from difficult situations, getting him or her to stop use could worsen the client’s subjective experience of distress.

Concurrent substance use and mental health problems also vary in severity. Most mental health services are directed toward helping people who have severe mental illnesses. It is the substance use problems of this population that have had the most influence on the ways that mental health providers have approached concurrent disorders. On the other hand, the addiction treatment system works with people whose substance use problems usually range from moderate to severe. There, the prevalence of mood, anxiety and anger problems has informed the ways that addiction professionals have viewed concurrent disorders (Prim et al., 2000). Thus the treatment setting, and the identified characteristics of the population seeking help in that setting, influence the choice of screening, assessment and treatment approaches.

The four-quadrant framework, developed by the U.S. National Association of State Mental Health Program Directors (NASMHPD) and National Association of State Alcohol and Drug Abuse Directors (NASADAD) Joint Task Force, and adopted by the Substance Abuse and Mental Health Services Administration (Substance Abuse and Mental Health Administration, SAMHSA, 2003), illustrates the range and severity of concurrent disorders within both the mental health and the substance use treatment populations. The framework relates systems of care to problem severity and is intended to help substance use and mental health providers “organize the range of services that can best meet the needs of the individuals with multiple symptoms and varying degrees of severity” (SAMHSA, 2003, p. 59).

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