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Symptoms & Signs of Dual Diagnosis & Co-Occurring Disorders

Dual diagnosis is a term that describes the simultaneous presence of a substance use disorder (substance abuse or addiction) and some form of diagnosable mental illness. Doctors and other mental health professionals also refer to these overlapping conditions as co-occurring disorders. Since dual diagnosis can involve any addictive substance and any form of mental illness, symptoms of the condition vary widely from person to person.

What Is Substance Use Disorder?

All people with a substance use disorder (SUD) are engaged in the dysfunctional and inappropriate consumption of a substance capable of triggering addiction. The long list of these substances includes alcohol; illegal drugs such as heroin, cocaine and methamphetamine; and prescribed medications such as opioid painkillers, ADHD stimulant medications and benzodiazepine tranquilizers. Some affected individuals abuse alcohol, a drug or medication, but haven’t undergone the brain changes that lead to full-blown addiction. Other affected people have undergone these brain changes.

At one time, doctors made a clear distinction between substance abuse and substance addiction. However, there is now a general understanding that the symptoms of abuse and addiction can appear together in a wide variety of combinations. For this reason, the official definition of substance use disorder does not distinguish between abusive, non-addicted substance consumption and addicted substance consumption. There are currently eight specific forms of SUD, each named for an addictive substance or group of substances.

Mental Illnesses Associated With Substance Abuse/Addiction

People with a substance use disorder are far more likely to experience certain forms of mental illness than the rest of the population. In descending order, the illnesses most frequently associated with SUD and dual diagnosis are bipolar I disorder, bipolar II disorder, schizophrenia and major depression (major depressive disorder). Roughly 33% of all people with a diagnosable mental health condition also have some form of substance use disorder. In people with severe mental health conditions, the rate of SUD is an even higher 50%.

Substance-Related Symptoms

The specific symptoms of substance abuse and addiction can vary widely from person to person, and depend to some extent on the type of substance consumed. However, we can still identify some general symptoms that tend to appear in affected individuals. Common problems you or your loved one may encounter include:

  • Repeated use of a substance in high-risk situations
  • An inability to control the rate or amount of substance intake
  • Isolation from family, friends or other support networks
  • Unexplained or rapidly developing changes in attitude or behavior
  • Increasing tolerance of the effects of substance use
  • The onset of withdrawal symptoms when substance use stops or decreases
  • Reliance on a substance in order to feel “normal”
  • Strong cravings for a given substance
  • Continued substance intake even when this intake causes serious personal, social, school-related or work-related problems
  • Devotion of significant time to obtaining a substance, using a substance and/or recovering from episodes of substance use

A person with mild SUD has only two or three symptoms, while a person with severe SUD has at least six. Moderately affected individuals fall in the middle of these two extremes.

Mental Health-Related Symptoms

Each form of diagnosable mental illness produces its own unique symptoms. Let’s look at the symptoms of the four conditions most likely to appear in people with co-occurring disorders.

Bipolar I Disorder — People with bipolar I disorder experience relatively brief bouts of an unusually “up” or excitable state called mania, as well as generally longer bouts of major depression. Mania symptoms include jitteriness, a reduced need for sleep, elation, increased talkativeness and an inflated sense of self. Depression symptoms include a notably “down” mood, appetite changes, changing sleep patterns, feelings of sadness and/or worthlessness and (in some people) suicidal thought, planning or action.

Bipolar II Disorder — People with bipolar II disorder also experience bouts of major depression. However, instead of fully developed mania, they experience bouts of a more subdued state called hypomania.

Schizophrenia — The hallmark symptom of schizophrenia is psychosis, a mental state that can include hallucinations with or without delusional patterns of thought, as well as unusually disorganized thought/speech and uncontrolled changes in normal body movement. Other possible symptoms include emotional flatness, an inability to experience pleasure and problems with attention and memory.

Major Depression — People with major depression have the same types of depressive symptoms found in people with bipolar I disorder and bipolar II disorder. These symptoms remain active for at least two weeks at a time.


National Alliance on Mental Illness: Dual Diagnosis

University of Utah – Genetic Science Learning Center: Mental Illness – The Challenge of Dual Diagnosis

Substance Abuse and Mental Health Services Administration: Co-Occurring Disorders

U.S. National Library of Medicine: Mood Disorders

National Institute of Mental Health: Schizophrenia

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