Co-Occurring Disorders and Comorbidity

Read on to learn the common types, signs, causes, and treatment methods for co-occurring disorders.

Table of Contents

Overview of Co-Occurring Disorders

According to the Substance Abuse and Mental Health Services Administration’s (SAMHSA) 2020 National Survey on Drug Use and Health, about 35.9 million people had an acute mental illness, and 20.9 million had a substance use disorder. Although these numbers are worrisome, a third category stood out—about seventeen million adults had both a mental illness and a substance use disorder. This experience is known as a co-occuring disorder.1

The presence of both a mental health disorder and a substance use disorder (SUD) is called a co-occurring disorder. Having either a mental illness or a substance use disorder is a difficult situation that calls for treatment.

The Relationship Between Mental Illness and SUD

The relationship between mental illnesses and SUDs goes both ways. Co-occurring disorders heighten the risk of development and adverse effects from both disorders. For example, having a mental illness increases the risk of developing a substance use disorder—resulting in co-occurring disorders.

According to SAMHSA, adults eighteen years and older who have a serious mental illness are:1

Serious mental illnesses are defined as diagnosable mental disorders that severely affect and impair daily life.2

The Impact of Co-Occurring Disorders

The occurrence of either a mental illness or substance abuse can impair a person’s ability to function well and live a healthy life. However, a co-occurring disorder causes significant functional impairments and taxes an individual’s resources more deeply than one single disorder. Co-occurring disorders result in: 

Comorbidity vs. Co-occurring Disorders: Are They the Same?

When reading about mental illness and substance use disorders, the terms comorbidity and co-occurring disorders may appear often. Sometimes, they’re used interchangeably and, other times, they’re used as distinct terms. There is no solid answer because their use depends on the diagnosis and context. For the most part, most clinicians refer to the presence of a chronic physical condition (such as diabetes or high blood pressure) and another illness (either physical or mental) as comorbid disorders.

A mental illness that occurs simultaneously with a substance use disorder or another mental health condition is typically referred to as a co-occurring disorder. Some clinicians distinguish between the two by referring to severe comorbidity as illnesses that significantly affect the progress and prognosis of both. What’s important to remember is that, no matter what term is used, a substance use disorder or mental illness that occurs with another illness is inextricably linked and can complicate overall healing.

The Most Common Comorbidities

Research into SUD comorbidities indicate that the following mental illnesses commonly appear as co-occurring disorders: 

Anxiety Disorders Comorbidity

Studies show high rates of comorbid anxiety disorders with SUD. Thus, anxiety disorders, such as panic disorders, generalized anxiety disorder, post-traumatic stress disorder, and obsessive-compulsive disorder, are a common occurrence. In a 2020 study of one hundred participants with SUD, 67% displayed severe signs of anxiety.3

Mood Disorder Comorbidity

Mood disorders like bipolar disorder and depression occur at high rates in people with SUD. For example, about 50% of people with bipolar disorder will develop a substance use disorder sometime in their lifetime, causing bipolar disorder comorbidity.4

Schizophrenia Comorbidity

SUDs frequently occur in people with schizophrenia and worsen over the course of the disease. Studies indicate that people with schizophrenia are at high risk for SUD, perhaps as an attempt to self-manage the symptoms of their schizophrenia. 

Personality Disorder Comorbidity

Personality disorders are behaviors and experiences that highly deviate from cultural expectations. A few examples of personality disorders are narcissistic personality disorder, antisocial personality disorder, and borderline personality disorder.5

Antisocial personality disorder and borderline personality disorder occur most often as co-occurring disorders with SUD. About 34.8% to 73.0% of individuals with a personality disorder have an SUD, compared with only 10% to 14.8% in the general population.6

Note that the above comorbidities are the most common, but all mental health conditions can result in comorbidity.

Common Signs of Comorbidity

Spotting comorbidity signs can be difficult because they often overlap. So, it is important for family members and loved ones to develop an awareness of the signs of comorbidity symptoms. 

Common Signs of Mental Health Disorders

The following signs can occur in those suffering from mental health disorders:7

Common Signs of Substance Use Disorders

Below are the most common signs of a substance use disorder:8
Common Signs of Comorbidity

Comorbidity Causes and Risk Factors

Comorbidity occurs due to numerous factors, some perhaps happening well before adulthood. The following are a few common causes and risk factors for comorbidity. 

Adolescence and Young Adulthood

The teen years are a time for experimentation and exploration, but it’s also a time where risky decisions can lead to a lifetime of adverse consequences. Drug use can start at any point in a person’s life, but adolescence is an especially precarious time. According to the CDC, the risk of developing substance use disorder rises the younger an adolescent starts drinking alcohol or using substances. In addition, adolescence and young adulthood are typically when the first signs of mental illness appear, making this stage in life an exceptionally risky time for developing co-occurring disorders.9

Genetics and Family Inheritance

Mental illness is not solely due to genetics, but an estimated 40% to 60% of an individual’s risk for mental illness or SUD can stem from genetic vulnerabilities. Epigenetics is the study of how gene activity is influenced by environmental factors like trauma, chemical exposure, and chronic stress that can affect gene expression—ultimately impacting behavior and health. Complex interactions between the environment and a person’s genes can impact the development of co-occurring disorders, and researchers are still exploring all the ways this can happen.10

Brain Region Involvement

Areas in the brain that control decision-making, impulse control, and emotions have susceptibilities to mental illness, making it more likely that a person with mental illness develops an SUD. Conversely, brain areas involving neurotransmitters, such as dopamine, serotonin, and norepinephrine, are vulnerable to substance use exposure. Therefore, addictive substances can affect areas in the brain already made vulnerable due to mental illness, causing co-occurring disorders.10

Environmental Influences

Many environmental factors are risk factors for developing both SUDs and mental illnesses. For example, childhood trauma increases the likelihood of having a mental illness or SUD in adulthood, thus raising the risk for comorbidity. Additionally, chronic stress can affect mental health and exacerbate substance use, making stress a risk factor for comorbidity.10

Diagnosis and Co-Occurring Disorders Treatment

Comorbidity is best diagnosed and treated through an integrated approach, with both being addressed simultaneously. A thorough mental health exam, combined with the collection of a patient’s history, is necessary for comorbidity diagnosis. Because SUD and mental illness are so connected, a treatment plan that identifies, evaluates, and offers intervention for both at the same time is the ideal approach. In addition, a medical assessment may be warranted to rule out any physical illnesses or health conditions. 

Comprehensive assessment tools allow clinicians to effectively obtain the proper diagnosis and target treatments. Though a diagnosis is challenging at first, acquiring sufficient information and having enough time for observation can offer a more accurate diagnosis for comorbidity. For treatment, effective methods that consider mental health and substance use disorders include medication and psychotherapy.

Hope for People With Comorbidity

Excluding one condition and treating the other increases the chances of relapse and makes recovery more challenging than it needs to be. While individuals with comorbidity may have two or more conditions, substance use and mental health disorders can be treated simultaneously. Integrated treatment for co-occurring disorders treats an SUD and mental illnesses together rather than in isolation. By addressing and treating both disorders, it raises the chances for a successful long-term recovery.

The PAC Program provides an integrated approach for co-occurring disorder treatment. Our trained professionals offer a comprehensive initial assessment that expertly identifies co-occurring disorder symptoms. We allow our clients to recover in a supportive and caring atmosphere, giving the one-to-one attention necessary for long-term recovery. Contact us at The PAC Program and let us help you or your loved one through the treatment process. 


If you or a loved one needs help, please call us at
623-523-4748 and our team at Blueprints For Recovery in Arizona will help.

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