What is Dual Diagnosis? When Addiction and Mental Illness Co-Occur

Addiction and mental illnesses commonly occur together. When they do, it’s known as a dual diagnosis, or co-occurring disorders. Dual diagnosis requires specialized treatment that addresses both disorders. Since dual diagnosis is common, it’s not difficult to find a program that treats both addiction and mental illness.

If you or someone you love has been diagnosed with co-occurring disorders or you suspect a dual diagnosis, it’s important to understand both addiction and mental illness, including how they occur, how they’re diagnosed and how they’re best treated.

What is Mental Illness?

According to the American Psychiatric Association, around one in five adults–20 percent of the population–has some form of mental illness. 1 Mental illnesses cause changes in thought patterns, emotions, or behaviors– or all three. It can interfere with healthy social functioning and reduce feelings of good health and wellbeing. The most common mental illnesses are anxiety and depression. In any given year, around 40 million Americans are living with an anxiety disorder, and nearly 15 million suffer from depression.

Mental illness is highly treatable, but many people who have a mental illness don’t seek help because it is still a misunderstood and vilified diagnosis. Stigma against mental illness is still prevalent in modern society, even though mental illnesses are medical conditions that just happen to affect the brain instead of another organ like the heart or liver.

The best treatment for mental illness is a combination of medication and counseling. Medication properly balances brain chemicals, while counseling helps teach skills and strategies for coping with and reducing symptoms.

What is Addiction?

Addiction is widely considered to be a brain disease because it changes the physical structures and chemical functions of the brain. These changes lead to compulsive drug abuse despite the negative consequences it causes. Someone struggling with addiction will be unable to quit using drugs or alcohol despite wanting to quit or trying to stop. The National Institute on Drug Abuse stresses that once an addiction develops, good intentions and willpower are not enough to end it for the long-term. 2 It almost always requires professional help.

Addiction is highly complex. It almost always has underlying issues, which often include a history of trauma, chronic stress, family dysfunction or mental illness. These issues must be addressed in order to effectively treat an addiction. Additionally, addiction does serious damage to many areas of life. It causes dysfunction in relationships and can lead to financial and legal troubles. It does a number on health and wellbeing. Successfully treating an addiction requires repairing the damage it has done. Finally, addiction changes thought and behavior patterns and leads to dysfunctional ways of thinking and behaving. Central to successful recovery is identifying these harmful patterns and learning to think and behave in healthier ways.

Dependence vs. Addiction

Dependence often occurs with addiction, but it’s not the same thing as addiction. Dependence is a physical reliance on drugs or alcohol characterized by withdrawal symptoms that set in when using stops. Dependence occurs as the result of the brain changing its chemical function in order to compensate for heavy substance abuse. This causes tolerance, which means that it takes increasingly larger doses to get the same effects. But as more is used, the brain continues to compensate, and at some point, brain function may shift so that it now operates more comfortably when the substance is present. Then, when use suddenly stops, normal brain function rebounds, and this sudden change in neurotransmitter activity produces physical withdrawal symptoms.

Addiction and dependence are diagnosed under the umbrella of “substance use disorder.”

The Prevalence of Dual Diagnosis and How it Occurs

According to the National Alliance on Mental Illness, around one-third of people who have any type of mental illness, and half of those with a serious mental illness, also have a substance use disorder. 3 Conversely, around one-third of people who abuse alcohol and over half of people who abuse drugs also have a mental illness.

How they Interact

The link between mental illness and substance abuse is well-established. Three scenarios help scientists understand the link:

  1. Abusing drugs or alcohol almost always makes a mental illness worse, and it can cause a new mental illness to occur.
  2. People who have a mental illness often use drugs or alcohol to self-medicate symptoms, such as using drugs or alcohol to reduce social anxiety or feelings of depression.
  3. Some people are at a higher risk of developing both addiction and mental illness due to overlapping factors.

Overlapping Factors

Overlapping factors for dual diagnosis include:

  • Genetic risks. Several regions of the human genome are associated with both mental illness and substance abuse.
  • Involvement in similar brain regions. Some brain regions are involved in both addiction and mental illness, such as the dopamine system, which is a factor in the development of both addiction and depression.
  • Environment. Environmental factors, such as chronic stress, can influence the development of both addiction and mental illness.

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Mental Illnesses that Commonly Occur with Addiction

While any mental illness can co-occur with a substance use disorder, some are more commonly associated with addiction than others.


Anxiety disorders include social anxiety disorder, generalized anxiety disorder and panic disorder. People with anxiety disorders often use drugs or alcohol to produce feelings of calm.

Depression and Bipolar Disorder

Depressive disorders include major depression and bipolar disorder, which are associated with a higher risk of substance abuse as a form of self-medication. A study published in the journal Psychiatric Clinics of North America found that nearly half of all people with bipolar disorder have a lifetime history of addiction. 4

Obsessive-compulsive disorder (OCD)

Obsessive-compulsive disorder causes uncontrollable and repetitive thoughts and behaviors. People with OCD often use drugs or alcohol to reduce intrusive thoughts and compulsive behaviors.

Eating disorders

Anorexia, bulimia and binge eating disorder are the three most common eating disorders, and they often co-occur with addiction. People who have an eating disorder may abuse drugs or alcohol to control their appetite, cope with low self-esteem or reduce feelings of depression. According to an article in the journal Social Work, around half of all people with an eating disorder abuse drugs or alcohol, compared with just nine percent of the general population. 5

Post-traumatic stress disorder (PTSD)

Post-traumatic stress disorder (PTSD) often occurs after a trauma and is characterized by symptoms like insomnia, nightmares, flashbacks and fear. PTSD is closely associated with substance abuse as a way to reduce the severity of symptoms and block troubling memories.

How Co-Occurring Disorders Are Diagnosed

Diagnosing co-occurring disorders can be challenging since symptoms of mental illness and addiction may overlap. Several assessments are used in a treatment or mental health setting to help care providers determine whether a mental illness is present and if so, whether the mental illness led to the addiction or vice-versa.

Intake assessments typically include an evaluation of current symptoms, a medical history and a mental illness history. The assessment helps care providers determine the severity of each disorder and develop a comprehensive, individualized, dual diagnosis treatment plan.

Because dual diagnosis is so common, both mental health and substance abuse treatment settings use integrated screening to help make the diagnosis. The simple screening helps providers determine whether a more comprehensive assessment is needed.

Integrated Treatment Offers Better Outcomes

Treating just a mental illness will do little to end an addiction, and treating just an addiction will do little to heal the mental illness. Successful recovery from a dual diagnosis requires integrated treatment that treats both disorders at the same time, taking into account both conditions.

Integrated treatment is a collaboration among treatment teams and provides a holistic approach to treatment. According to the Substance Abuse and Mental Health Services Administration, integrated treatment:

  • Reduces substance abuse
  • Improves symptoms of mental illness
  • Increases mental functioning
  • Reduces hospitalization
  • Increases stability in the client’s life
  • Results in fewer legal troubles
  • Improves clients’ overall quality of life

Holistic Treatment

A holistic treatment approach offers the best treatment outcomes. This approach involves a variety of traditional and complementary therapies and other interventions. These approaches address a wide range of issues of body, mind and spirit for whole-person healing.

Traditional Therapies

Traditional therapies include cognitive-behavioral therapy, dialectical behavioral therapy, acceptance and commitment therapy and pharmacotherapy, or the use of medications to treat symptoms of mental illness. Traditional therapies focus on helping people learn to better manage their thoughts, emotions and behaviors.

Complementary Therapies

Complementary therapies include art or music therapy, mindfulness meditation and restorative yoga. Complementary therapies improve self-awareness, self-esteem and self-confidence and provide clients with new ways to look at old issues.

Other Interventions

Other interventions and services in a holistic program are used as needed to ensure all needs are addressed. These interventions include psychoeducational classes that help people better understand dual diagnosis; vocational or educational assistance; legal help; and assistance with finding safe housing.

Goals of Treatment

Through a variety of therapies, individuals in dual diagnosis treatment:

  • Address underlying issues behind the addiction and mental illness
  • Develop coping skills for dealing with mental illness symptoms, cravings, stress and other relapse triggers
  • Identify troublesome thought and behavior patterns and develop new, healthier ways of thinking and behaving
  • Learn to relax and have fun without drugs or alcohol
  • Find purpose and meaning in a life of sobriety
  • Develop crucial life skills for successful independent living
  • Repair damaged relationships and restore function to other areas of life
  • Learn about addiction and mental illness, including how they develop, how they’re treated and how people enjoy long-term recovery from their diagnoses

Staying in treatment for an adequate period of time is essential for successful recovery. The National Institute on Drug Abuse stresses that anything less than 90 days is of limited effectiveness. This is especially true for people with a dual diagnosis.

Dual diagnosis treatment works for most people who engage fully with their treatment plan and stay in treatment for the duration of the program. Treatment helps people improve their thought and behavior patterns and develop the skills and strategies they need to recover from both a mental illness and a substance use disorder. Treatment can help you find peace and clarity in your life, improve quality of life and provide a greater sense of happiness and wellbeing.