Combined treatment

This page is reference information compiled from the cited sources. It is not medical advice. For any decision about health, diagnosis or care, consult a qualified professional.

What it is

Dual diagnosis, also called co-occurring disorders or dual pathology, is the condition of having a mental illness and a comorbid substance use disorder. The concept can be used broadly, for example depression and alcohol use disorder, or it can be restricted to specify severe mental illness and substance use disorder, or a person who has a milder mental illness and a drug dependency. Diagnosing a primary psychiatric illness in people who use substances is challenging as substance use disorder itself often induces psychiatric symptoms. The identification of substance-induced versus independent psychiatric symptoms or disorders has important treatment implications and often constitutes a challenge in daily clinical practice. Research instruments are also often insufficiently sensitive to discriminate between independent, true dual pathology, and substance-induced symptoms.

Key facts

Those with co-occurring disorders face complex challenges, including increased rates of relapse, hospitalization, homelessness, and HIV and hepatitis C infection compared to those with either mental or substance use disorders alone. Comorbidity of addictive disorders and other psychiatric disorders is very common, with a large body of literature demonstrating a strong association. Adolescents and young adults are particularly at risk for dual diagnosis, as early substance use can interfere with brain development and exacerbate emerging mental health conditions. The 2011 USA National Survey on Drug Use and Health found that 17.5% of adults with a mental illness had a co-occurring substance use disorder, representing 7.98 million people. Estimates in Canada are higher, with an estimated 40-60% of adults with a severe and persistent mental illness experiencing a substance use disorder in their lifetime. A study found that 47% of clients with schizophrenia had a substance misuse disorder at some time in their life. Only a small proportion of those with co-occurring disorders actually receive treatment for both disorders, with a 2011 estimate that only 12.4% of American adults with co-occurring disorders were receiving both mental health and addictions treatment.

When to seek professional help

The source text associates professional care with the diagnosis and treatment of dual diagnosis, or co-occurring disorders. Professional help is implicated when an individual has a mental illness and a comorbid substance use disorder. The source describes situations where diagnosing a primary psychiatric illness in people who use substances is challenging, necessitating professional differentiation between substance induced and pre-existing mental illness. Professional assessment is needed as substance use disorders can induce symptoms resembling mental illness, and psychiatric disorders among people who use substances often disappear with prolonged abstinence. Structured diagnostic instruments have been developed to increase diagnostic validity, and clinicians must make judgments on the origin of symptoms. Clients with co-occurring disorders face challenges accessing treatment, as they may be excluded from mental health services if they admit to a substance use problem and vice versa, indicating a need for coordinated professional care.

Source: Dual diagnosis (CC BY-SA 4.0 (Wikipedia)), retrieved 2026-09-22.