Why Mental Health Disorders Co-Exist With Substance Use

The numbers do not lie. Mental illness and addiction often overlap. In fact, nearly 9 million people have a co-occurring disorder according to the Substance Abuse and Mental Health Services Administration. Yet, only 7 percent of these individuals get treatment for both conditions. And nearly 60 percent receive no treatment at all.

Understanding Comorbidity

Comorbidity refers to the fact that two conditions, such as a specific mental health disorder and a substance use disorder, often co-exist together. What this means is that in many people with addictions, there is an underlying mental health issue as well. While neither condition actually causes the other, they do often exist together. What's more, one condition can exacerbate the symptoms of the other.

To better understand how comorbidity is possible, it helps to recognize that both are chronic brain disorders. In other words, when someone struggles with an addiction, their brain has been permanently rewired by the substance they abused. This, in turn, causes the brain to function differently than before. Just like diabetes or heart disease, a person with an addiction must manage their condition for the rest of their life. It is not as simple as stopping the drug use or alcohol condition. Many times, this is simply not possible.

Likewise, the changes that take place in the brain due to substance abuse occur in the same brain areas that are impacted by depression, anxiety, schizophrenia, and bipolar disorder. Consequently, it should not be surprising that there is a high rate of comorbidity between addiction and other mental illnesses. While the link is complex, some mental health issues increase the risk factors for substance abuse. What this means is that some people with mental illnesses will turn to alcohol or drugs to cope with the pain of their mental health issues.

Why Addiction and Mental Illness Co-Occur

Even though there is a high rate of comorbidity between addiction and mental illness, it does not mean that one necessarily caused the other—even if one condition appeared first. Instead, there are still a number of factors that need to be considered, according to the National Institute on Drug Abuse. For instance:

• Drug abuse can cause people to experience one or more symptoms of another mental illness. For example, there is an increased risk of psychosis in some marijuana users.
• Mental disorders can lead to drug or alcohol abuse because some people use substances to self-medicate. For instance, the nicotine in tobacco products sometimes lessen certain symptoms of schizophrenia and may improve cognition.

There also is some evidence that indicates that addictions and mental illnesses are caused by underlying brain deficits, genetic influences, and/or exposure to trauma early in life.​ For instance, it is estimated that 40 to 60 percent of a person's vulnerability to addiction can be attributed to genetics. There also are several regions of the human genome that have been linked to an increased risk both for substance abuse and mental illness.

Another common factor between mental health issues and addiction is the age at which the symptoms appear. During the teen years, people are still developing, maturing, and growing. As a result, significant changes in the brain occur during adolescence. For instance, teenagers are more prone to take risks and act impulsively. These behaviors, while common among teens, can influence the risk of addiction and other mental disorders.

Finally, people who are physically or emotionally traumatized are at a much higher risk of substance use disorders. This connection is particularly concerning for veterans returning to the country. In fact, one in five military servicemen and women coming back from Iraq and Afghanistan have reported symptoms of post-traumatic stress disorder (PTSD) or major depression.

Why It Is Difficult to Diagnose Both Conditions

Co-occurring disorders are sometimes difficult to diagnose. One reason is that the symptoms are often complex and can vary in severity. As a result, it is not uncommon for people to receive treatment for one disorder while the other disorder remains untreated. Sometimes this happens because the symptoms are so similar or overlap. In other words, both mental health issues and addiction can have similar biological, psychological, and social components.

Another reason for not diagnosing both conditions might include inadequate training or screening. In any case, the consequences of undiagnosed, untreated, or undertreated co-occurring disorders can lead to a higher likelihood of experiencing homelessness, jail time, medical illnesses, and even suicide.

What's more, people with mental health issues who also abuse substances like drugs or alcohol are at an increased risk for impulsive or violent acts, potentially landing them in legal trouble. Achieving lasting sobriety is increasingly difficult for them.

Treatment When Comorbidity Exists

Research suggests that co-occurring conditions need to be treated at the same time. In fact, for the best outcome, it helps when people with both an addiction and a mental health issue receive integrated treatment. With integrated treatment, doctors and counselors can address and treat both disorders at the same time. This, in turn, often lowers treatment costs and creates better outcomes for patients.

What's more, early detection and treatment of both conditions can greatly improve the person's recovery and quality of life. However, it is important to note that people who have both an addiction and another mental illness often have symptoms that are more persistent, severe and resistant to treatment compared with patients who have either disorder alone. For this reason, maintaining sobriety may be very difficult for them.

A Word From Verywell

Making a correct diagnosis of both an addiction and a mental health issue is vitally important to a patient's success. When this occurs, their chance of recovery increases. ​But there needs to be increased awareness of comorbidity for this to occur. Too many times, one of the conditions goes undiagnosed and untreated. As the recognition and treatment for co-existing conditions improves, this will help reduce the social stigma that makes people so reluctant to pursue the treatment that they need.