Co-Occurring Disorders

Just as the field of treatment for substance use and mental disorders has evolved to become more precise, so too has the terminology used to describe people with both substance use and mental disorders. The term co-occurring disorders replaces the terms dual disorder or dual diagnosis. These latter terms, though used commonly to refer to the combination of substance use and mental disorders, are confusing in that they also refer to other combinations of disorders (such as mental disorders and mental retardation).

Furthermore, the terms suggest that there are only two disorders occurring at the same time, when in fact there may be more. Clients with co-occurring disorders (COD) have one or more disorders relating to the use of alcohol and/or other drugs of abuse as well as one or more mental disorders. A diagnosis of co-occurring disorders occurs when at least one disorder of each type can be established independent of the other and is not simply a cluster of symptoms resulting from the one disorder.

Although co-occurring disorder is the most current term used professionally, for the purposes of this article, dual disorders will be used interchangeably.

The acronym MICA, which represents the phrase Mentally Ill Chemical Abusers, is occasionally used to designate people who have a COD and a markedly severe and persistent mental disorder such as schizophrenia or bipolar disorder. A preferred definition is mentally ill chemically affected people, since the word affected better describes their condition and is not pejorative. Other acronyms include: MISA (mentally ill substance abusers), CAMI (chemical abuse and mental illness), SAMI (substance abuse and mental illness), MISU (mentally ill substance using), MICD (mentally ill chemically dependent) and ICOPSD (individuals with co-occurring psychiatric and substance disorders).

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Common examples of co-occurring disorders include the combinations of major depression with cocaine addiction, alcohol addiction with panic disorder, alcoholism and polydrug addiction with schizophrenia, and borderline personality disorder with episodic polydrug abuse. Although the focus of this is on dual disorders, some patients have more than two disorders. The principles that apply to dual disorders generally apply also to multiple disorders.

The combinations of COD problems and psychiatric disorders vary along important dimensions, such as severity, chronicity, disability, and degree of impairment in functioning. For example, the two disorders may each be severe or mild, or one may be more severe than the other. Indeed, the severity of both disorders may change over time. Levels of disability and impairment in functioning may also vary.

Thus, there is no single combination of dual disorders; in fact, there is great variability among them. However, patients with similar combinations of dual disorders are often encountered in certain treatment settings.

More than half of all adults with severe mental illness are further impaired by substance use disorders (abuse or dependence related to alcohol or other drugs).

Compared to patients who have a mental health disorder or a COD use problem alone, patients with dual disorders often experience more severe and chronic medical, social, and emotional problems. Because they have two disorders, they are vulnerable to both COD relapse and a worsening of the psychiatric disorder. Further, addiction relapse often leads to psychiatric decompensation, and worsening of psychiatric problems often leads to addiction relapse. Thus, relapse prevention must be specially designed for patients with dual disorders. Compared with patients who have a single disorder, patients with dual disorders often require longer treatment, have more crises, and progress more gradually in treatment.

Psychiatric disorders most prevalent among dually diagnosed patients include mood disorders, anxiety disorders, personality disorders, and psychotic disorders.

Co-Occurring Disorders. Last reviewed 12/31/1969
  • American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition
  • Office for Treatment Improvement, Alcohol, Drug Abuse, and Mental Health Administration
  • Substance Abuse and Mental Health Services Administration (2005)
  • Hospital and Community Psychiatry
  • Dual Diagnosis of Major Mental Illness and Substance Disorder
  • Journal of the American Medical Association
  • Journal of Addictive Diseases
  • Archives of General Psychiatry
  • Center for Substance Abuse Treatment
  • Charney DA, Paraherakis AM, Gill KJ. Integrated treatment of comorbid depression and substance use disorders. Journal of Clinical Psychiatry. 62((9)):672-677; 2001.
  • Saxon AJ, Calsyn DA. Effects of psychiatric care for dual diagnosis patients treated in a drug dependence clinic. American Journal of Drug and Alcohol Abuse. 21((3)):303-313; 1995.
  • Etheridge RM, Hubbard RL, Anderson J, Craddock SG, Flynn PM. Treatment structure and program services in the Drug Abuse Treatment Outcome Study (DATOS). Psychology of Addictive Behavior. 11((4)):244-260; 1997.
  • Simpson DD, Joe GW, Rowan-Szal GA. Drug abuse treatment retention and process effects on follow-up outcomes. Drug and Alcohol Dependence. 47((3)):227-235; 1997b.