There is a strong link between mental illness and substance abuse. Quite often, an underlying mental health condition can lead people to self-medicate with drugs or alcohol to relieve their symptoms. These substances can cause serious mental health conditions with long-term use. Because of this connection, it’s not uncommon to struggle with a mental illness and substance use disorder at the same time. There are three terms often used to describe this occurrence: comorbidity, dual diagnosis, and co-occurring disorders. Terms “dual Diagnosis” and “co-Occurring disorders” are often used interchangeably when referring to someone who has both an addiction to drugs or alcohol and other mental health conditions. However, there are differences between co-occurring disorders and dual diagnosis. It’s important to know how they vary, especially if you are seeking treatment for addiction and mental illness.

Dual Diagnosis, Co-Occurring Disorders

What Is a Dual Diagnosis?

The term “dual diagnosis” refers to having two or more conditions simultaneously, as distinct diagnoses. It is also appropriate when more than two conditions exist. For example, a person could be diagnosed with both a mental disorder and a substance use disorder, or both diabetes and high blood pressure.

Dual diagnosis was first used in the 1980s to refer to individuals with severe mental illness and substance use disorders. Today, the Substance Abuse and Mental Health Services Administration (SAMSHA) prefers the term co-occurring disorders.

Dual diagnosis is a more general term for two or more conditions that occur in the same person at the same time, whether physical or mental. The presence of heart disease and diabetes could be considered a dual diagnosis. Today, dual diagnosis treatment is the term most often used to describe how those who have both a mental illness and addiction are treated.

What Is a Co-Occurring Disorder?

As we already mentioned above, dual diagnosis was first identified in the 1980s among individuals with coexisting severe mental illness and substance abuse disorders. Today, the Substance Abuse and Mental Health Services Administration (SAMSHA) uses the term co-occurring disorders (COD) to refer to the aforementioned concurrent disorders. COD is defined as co-occurring substance-related and mental disorders. Patients said to have co-occurring disorders have one or more substance-related disorders as well as one or more mental disorder

To be diagnosed with a co-occurring disorder, both conditions must exist independently: Neither can simply be a cluster of symptoms caused by the other. In this case, either substance use or mental illness can present first. Interactions between the two disorders can worsen the course of each of them. The most common combination is a severe substance use disorder and a mild-to-moderate severity mental disorder. For example, having an alcohol use disorder (AUD) along with attention deficit disorder (ADD) or anxiety disorder.

Why Do Disorders Often Co-Occur?

About half of all people diagnosed with mental illness or substance use disorder will develop at least one co-occurring disorder in their lifetime. Both genetics and environmental factors may contribute to this increased risk. If a person has a mental illness or a substance use disorder, why might they be at a higher risk for the other?

Biology and Genetics

Both mental illness and substance use disorders are biologically based. As a result, inheriting certain genes may increase the risk of both issues. Genetic predisposition accounts for approximately 40 to 60 percent of an individual’s vulnerability to substance use. In a study of families severely affected by alcohol use disorders, approximately half of the brothers and 22-25 percent of the sisters of an affected sibling were also affected. In adoption studies, children adopted from parents with alcohol use disorders have a higher risk of developing that disorder than children adopted from families in which alcohol use is not a problem.

Environmental Triggers

Environmental factors may also increase the risk of both mental illness and substance use disorders. Such triggers might include:

  • Chronic stress: Stress alters the brain’s responses, resulting in a decreased ability to control behavior and an increase in impulsivity. When people self-medicate to relieve symptoms of stress, they increase their risk of developing alcohol and substance use disorders6. Stress can also affect the release of dopamine, a neurotransmitter that impacts how drugs affect the brain.
  • Trauma (as physical or sexual abuse): People who have experienced physical or emotional trauma are at much higher risk for drug use and substance use disorders. Individuals with post-traumatic stress disorders (PTSD) may use substances to cope with their anxiety.


Genetic and environmental triggers do not work in isolation. Epigenetics is the study of how factors such as chronic stress, trauma, or drug exposure can alter the way genes are expressed. Each individual inherits an alphabet-like genetic sequence from their parents. It turns out that changes in a cell’s environment can affect how these genes are read and acted upon, and affect how your body functions. For example, when alcohol is metabolized, acetate is formed. According to research on mice, when acetate reaches the brain it directly alters proteins that regulate genetic functions. These changes affected the mice’s behavior when they were given certain environmental cues9. This may partially explain why some people are more vulnerable to environmental drinking triggers than others.


Many people with mental illnesses use alcohol or drugs to ease their symptoms. This is often referred to as “self-medicating.” Substance abuse can help control the symptoms of a mental illness at the moment, but in many cases, it can also exacerbate the symptoms, especially in the big picture.

Brain Development

Brain cells, called neurons, have a fatty coating (myelin) around the transmitting part of the cell. Like insulation, myelin speeds up the transmission of nerve impulses throughout the brain. Myelinating neurons takes time. The brain is not fully myelinated until around age 25. Circuits that control executive functions such as decision making, emotions, and impulse control are the last to be myelinated fully10. Substance use before age 25 is a risk factor for developing substance use disorders because chemicals can adversely affect a developing brain. It may also be a risk factor for developing mental illnesses.

Brain Chemistry

Substance use can alter one’s brain chemistry, increasing the risk of mental illness by triggering symptoms in genetically predisposed people. Alcohol, for example, increases the release of dopamine, a chemical messenger in the brain that activates a person’s reward circuits12. This causes a feeling of pleasure and gets encoded as a pleasant memory, contributing to habit development. Over time, the brain adapts to the excess dopamine, and alcohol has the opposite effect, causing dopamine levels to fall rapidly. Dopamine affects mood, memory, movement, motivation, and behavioral reinforcement. Thus, alcohol’s impact on dopamine affects the same areas of the brain as mental disorders like schizophrenia, anxiety, mood disorders, and impulse control disorders.

Co-occurring disorders treatment.

Individuals diagnosed with co-occurring disorders often need more intense treatment due to the complexity of their case emphasizing the importance for clinicians to provide effective and efficient treatment to these patients. Individuals diagnosed with co-occurring disorders face greater consequences from substance abuse compared to those patients diagnosed with only a mental illness such as schizophrenia or bipolar disorder.

Whether you want to call it dual diagnosis or co-occurring disorder, correct diagnosis and treatment are essential. It can be difficult to untangle many of the overlapping symptoms of drug or alcohol abuse and certain mental health disorders to ensure appropriate care. That’s why you need a treatment center, like Crosspointe recovery, that understand the nuances of co-occurring disorders treatment. At Crosspointe recovery, we specialize in evidence-based treatment to ensure you get the highest quality of care. If you believe that your mental health condition has contributed to a substance abuse disorder or vice versa, we’re here to help. Contact us today!


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