Mental Illness and Substance Abuse Comorbidity: A Review

Introduction: The Mental Illness–Substance Abuse Relationship

Does mental illness cause substance abuse addiction, or does substance abuse addiction cause a mental illness diagnosis? Does the relationship go both ways?

A complex relationship exists between substance abuse and mental illness. Those suffering from depression, anxiety, and other mental illnesses may use alcohol and drugs as a form of self-medication. Unfortunately, though such options may appear to work temporarily, substance abuse is no treatment for any condition. In fact, it often aggravates the problem — both during severe intoxication and in the course of substance withdrawal (NAMI, 2010).

Furthermore, alcohol and drugs can initiate mental illness in persons who are otherwise mentally healthy, while worsening existing problems in those who are already mentally ill. Active substance users tend not to follow through properly with therapy and are more vulnerable to serious health complications and even premature death. Those with a dual diagnosis are also more prone to violent and impulsive behavior and less likely to attain long-term sobriety. Alcohol and drug addicts have a greater likelihood of committing suicide, and such individuals usually experience severe substance-abuse-related complications, legal problems, and physical dependency (NAMI, 2010).

Scope, Affected Populations, and Significance

Scope of the Problem

Nearly half of all individuals suffering from severe mental illness are also drug or alcohol addicts. Thirty-seven percent of alcohol dependents/abusers and 53% of drug dependents/abusers also suffer from at least one mental health issue (NAMI, 2010). In 2013, 359,000 U.S. adolescents (1.4%) aged 12–17 years concurrently suffered from a major depressive episode (MDE) and a substance use disorder (SUD). In that same year, 7.7 million adults (3.2%) in the U.S. aged 18 and above simultaneously suffered from SUD and any mental illness (AMI), while 2.3 million U.S. adults (1%) simultaneously suffered from serious mental illness (SMI) and SUD (Substance Abuse and Mental Health Services Administration, Center for Behavioral Health Statistics and Quality, 2014).

The Affected

Affected individuals suffer many serious consequences. Dual diagnosis can cause problems with decision-making, attention, and memory, thus affecting daily lives and functioning. Body organs are also affected. Such individuals are more likely to behave violently, refuse compliance with therapy, and fail to be treated successfully, compared to those having only one of the problems — mental illness or substance abuse. Dual-diagnosis-related issues impact families, colleagues, and friends as well. Individuals with a dual diagnosis are also prone to incarceration or homelessness. Approximately half of homeless individuals suffering from SMI also suffer from SUD. Additionally, an estimated 16% of prison and jail inmates have both SMI and SUD, and 72% of prisoners with mental illness suffer from SUD as well (NAMI, 2010; Langas, Malt, & Opjordsmoen, 2011).

Significance of the Problem

Individuals whose co-occurring problems are not treated are more likely to engage in violent acts, to fail to respond appropriately to therapy, and to become victims of illness, imprisonment, homelessness, and death. Their daily lives and functioning are adversely affected because of issues with decision-making, memory, and attention; substance abuse also adversely affects body organs (NAMI, 2010).

Relevance of the Problem

Several epidemiological and clinical studies have explored the issue of high comorbid mental illness frequency in substance dependents and abusers. These dual disorders must be given high priority because of the serious repercussions they pose for patients, families, society, and health services. Compared to those who suffer only SUD or SMI, dually diagnosed individuals experience delayed diagnosis, severe psychopathological problems, lesser treatment compliance, poorer treatment outcomes, greatly impaired social functioning, increased emergency admissions, greater physical comorbidity, homelessness, unemployment, suicidal ideation, and criminal or violent tendencies. All of these issues highlight the need for more extensive research in this area (Anderson, Ziedonis, & Najavits, 2014; Langas et al., 2011).

Research Objectives and Questions

This review aims to document and describe the patterns of comorbidity between SUD and mental disorders in the general population. The following research questions guide the inquiry:

1. What mental disorders are found, and how prevalent and severe are they among individuals admitted for the first time for substance use — admitted consecutively to specialist services within a single hospital catchment area?

2. What is the average duration of untreated SUD?

3. How prevalent is substance-independent versus substance-induced depression, as well as other Axis I illnesses, in those diagnosed with SUD?

4. Can any differences be found in mental disorder diagnoses among those using legal versus illegal substances?

5. Can any sociodemographic differences be found between individuals using legal and illegal substances?