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Symptoms & Signs of Dual Diagnosis & Co-Occurring Disorders

Dual diagnosis describes the simultaneous presence of substance use disorder and mental illness. This set of conditions may also be called a co-occurring disorder. Dual diagnosis can involve any addictive substance and any form of mental illness. The symptoms of the condition vary widely from person to person.

What Is Substance Use Disorder?

People with a substance use disorder engage in inappropriate use of an addicting substance. The long list of these substances includes alcohol, illegal drugs (heroin, cocaine, methamphetamine, etc.), and prescribed medications (opioid painkillers, ADHD stimulant medications, benzodiazepine tranquilizers, etc.).

Some affected individuals may abuse alcohol, an illicit drug or medication. but they may not have undergone the brain changes of an addiction. Other affected people have undergone these brain changes.

Mental Illnesses Associated With Substance Abuse/Addiction

People with a substance use disorder are more likely to experience mental illness than the rest of the population. Illnesses most frequently associated with substance use disorder and dual diagnosis include:

Roughly 33% of all people with a mental health condition also have a form of substance use disorder. In people with severe mental health conditions, the rate of substance use disorder is 50%.

Substance-Related Symptoms

The symptoms of substance abuse and addiction can vary widely from person to person. It may also depend on the type of substance consumed. We can still identify some 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 use causes serious personal, social, school-related or work-related problems
  • Devotion of significant time to obtaining a substance.
  • Using a substance or recovering from episodes of substance use

A person with mild substance use disorder has only two or three symptoms, while a person with a severe case 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 set of symptoms. Let’s look at the symptoms of the four conditions most likely to appear in people with co-occurring disorders.

Bipolar I Disorder. This is also referred to as manic-depressive disorder. Bipolar I disorder is characterized by brief bouts of an energetic or excitable state called mania. These patients have longer bouts of depression.

Mania symptoms include:

  • Jitteriness
  • A reduced need for sleep
  • Elation
  • Increased talkativeness
  • An inflated sense of self

Depression symptoms include:

  • A notably “down” mood
  • Appetite changes
  • Changing sleep patterns
  • Feelings of sadness or worthlessness
  • (In some people) suicidal thought, planning or action

Bipolar II Disorder. People with bipolar II disorder also experience bouts of major depression. But they experience less intense elevated moods called hypomania.

Schizophrenia. The main symptom of schizophrenia is psychosis. These individuals also have a mental state that can include hallucinations with or without delusional patterns of thought. Schizophrenia includes disorganized thought and speech. These people also experience 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 experience symptoms such as:

  • Daily fatigue or loss of energy
  • Regular feelings of worthlessness or guilt
  • Impaired concentration, indecisiveness
  • Insomnia or hypersomnia (excessive sleeping) almost every day
  • Markedly diminished interest or pleasure in almost all activities
  • Recurring thoughts of death or suicide
  • Significant weight loss or gain


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

Quello SB, Brady KT, Sonne SC. Mood disorders and substance use disorder: a complex comorbidity. Sci Pract Perspect. 2005;3(1):13-21.

Posted on September 22, 2016 and modified on April 27, 2019

Krisi Herron

Medically Reviewed by

Krisi Herron, LCDC

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