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Understanding Co-Occurring Disorders

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When someone suffers from a substance use disorder and a mental health or psychiatric disorder (such as depression, anxiety, PTSD, schizophrenia, OCD, or a personality disorder), the conditions are considered co-occurring because they are occurring at the same time.

Previously known as dual diagnosis, co-occurring disorders (COD) affected approximately 7.9 million adults in the U.S. in 2014, according the 2014 National Survey on Drug Use and Health.


It has further been discovered that about a third of all people experiencing mental illnesses and about half of people living with severe mental illnesses are also experiencing issues with substance abuse. The high correlation of substance use and mental illness is mirrored in the substance abuse community, where about a third of all those suffering with alcohol use disorder and more than half of those with drug use disorders report experiencing a mental illness.  

NAMI, the National Alliance on Mental Illness, reports that men are more likely to develop a COD than women, and that people with a lower socioeconomic status, military veterans, and people with general medical illnesses are at a particularly high risk of a COD diagnosis. Armed with the knowledge that those with co-occurring disorders also have increased rates of relapse, hospitalization, homelessness, and HIV and Hepatitis C infection make it more important that co-occurring disorders be properly diagnosed and treated.

Identifying the Root: Which Came First?

Researchers theorize that when a psychiatric disorder develops first, it may cause someone to use alcohol or drugs to self-medicate the symptoms of their condition. But sometimes, substance misuse develops first and the resulting substance use disorder leads to psychiatric illnesses because drugs affect brain chemistry, moods, behavior, and thoughts. Either way, when a psychiatric disorder co-exists with substance use disorder, the two conditions tend to exacerbate each another, which makes recovery from the substance use much more difficult to achieve.

The Relationship Between Substance Use & Psychiatric Disorders

There are a number of theories about the relationship between substance use and psychiatric disorders. One theory is the self-medication theory, which suggests that people with psychiatric disorders use alcohol and drugs to relieve the symptoms of their illness and/or to counter the side-effects of medications.

Another theory, the causality theory, suggests that substance use itself may cause a psychiatric disorder. The disruptive effect of narcotics on brain chemistry can have lasting effects that impact mood, behavior and decision making processes.

Professionals can't always pinpoint the exact cause of COD, but the volume of research in recent years brings hope to those with this condition and the importance in understanding it.

Treating Both Conditions Together

When someone is being evaluated for an alcohol or drug use disorder, it is important to determine if they also have a psychiatric disorder, and if possible, determine whether one is influencing the other.

When the treatment team is aware of both conditions, there can be an integrated treatment approach that addresses both the psychiatric disorder and the substance use issue simultaneously. The prescription of medications for psychiatric disorders will be made with consideration for risks of addictive properties, and addiction treatment modalities will be selected with consideration of previous trauma and mental health issues.

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