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A person suffering from substance abuse disorder and mental illness

What Is Comorbidity and How Does It Differ From Concurrent Disorders?

Relatives of individuals with drug dependence often wonder what made their loved ones abuse drugs. Did the substance abuse happen because they have a mental illness? Or did the substance abuse cause the mental illness?

Often, mental illness contributes to substance abuse and vice-versa. But sometimes, a person can have both substance abuse disorder and mental illness at the same time. This is what’s called a concurrent disorder.

What Is the Difference Between Concurrent Disorder and Comorbidity? 

What is comorbidity, and what is the difference between this and concurrent disorders

In Canada, comorbidity is another term used for concurrent disorders. Ultimately, they mean the same thing. 

In the United States, dual disorder, dual diagnosis, co-occurring disorder, and mentally-ill chemical abuse are the terms used interchangeably for concurrent disorder.

A Closer Look at Comorbid Substance Abuse Disorders

As previously mentioned, comorbidity is a condition where one person is suffering from both a mental illness and a substance abuse problem. 

Examples of comorbidities include a person with chronic depression who also engages in the problematic use of cannabis. This would then be called a comorbid substance disorder. If someone with Post-Traumatic Stress Disorder (PTSD) also engages in the problematic use of methamphetamine, this is also considered a comorbid disorder. 

Comorbidities can happen in four general ways:

Substance Abuse Comes First Before the Mental Illness

A person starts taking a substance that subsequently triggers symptoms of a mental illness like psychosis, depression, etc.

Mental Illness Comes First Before Substance Abuse

An individual with a mental illness uses alcohol or drugs to cope with the troubling symptoms of their mental illness.

Substance Abuse and Mental Illness Start at the Same Time

This occurs when a traumatic experience (e.g. a serious accident) triggers a substance disorder and a mental illness simultaneously.  

Substance Abuse and Mental Illness Start Sequentially

This occurs when both substance abuse and mental illness start separately but have the same risk factors, such as genes or a difficult environment. For example, some people have a specific gene that makes them more likely to develop a mental illness later in life if they’ve used marijuana when they were younger. There are genes that also influence how a person reacts to a drug. 

Comorbidity of Depression and Substance Abuse 

One of the most prevalent mental health problems in Canada is depression. Often, people diagnosed with depression also have substance use disorders and vice versa. This indicates that depression and addiction often go hand-in-hand. 

A woman suffering from depression, holding her face in her hands

But what is the relationship between depression and substance abuse? People diagnosed with clinical depression often have intense feelings of loneliness and hopelessness that last for months or even years.

And because they face an uphill battle everyday with the feeling that there is no end in sight, they turn to substances like alcohol and drugs to cope. Although it may lessen their burden, the relief it gives is temporary.

Aside from the fact that these substances are addictive, they can also trigger and exacerbate their depression. Over time, comorbidity of depression and substance abuse can lead to health problems and brain damage, reducing life expectancy by 10 to 20 years. 

It is also associated with an increased rate of social and personal impairment, other psychiatric conditions, and suicide.

How Comorbid Conditions are Diagnosed 

Diagnosing comorbid conditions is a complex process because many of the symptoms of substance abuse and mental illness look the same. 

An intoxicated person can look and act like a person with mental illness. And many mental diseases seem similar to drug or alcohol withdrawal symptoms.

It’s crucial to use all comprehensive assessment tools to decrease the chances of a missed diagnosis. For instance, a person entering a drug treatment facility must be observed after a period of abstinence to determine whether they are exhibiting symptoms of withdrawal or comorbid mental disorders.

The same goes for an individual entering treatment for a mental illness—they must also be screened for substance use disorders. Practicing this leads to a more accurate diagnosis and a more targeted treatment plan.

Although reaching an accurate diagnosis is complicated, it’s important to note that people with both substance use disorder and a mental illness typically exhibit more severe and persistent symptoms compared to those who just have one disorder. Generally, they are also more resistant to treatment. 

Treatments for Comorbid Substance Use Disorder and Mental Health Illness

The high comorbidity rate of substance use disorder and other mental illnesses calls for an accurate assessment and integrated treatment approach. Research shows it is superior compared to a separate treatment for each.

Collaboration between clinical providers, families of patients, and organizations that provide support services is essential. Explaining the treatment plan to the patient so that everything is clear to them makes them more likely to follow through.


There are various medications that are effective in treating some substance use disorders. This includes: 

  • Naltrexone
  • Bupropion HCI 

Behavioural Therapies

Behavioural therapies, whether alone or in combination with medication, have a high success rate for many individuals with comorbid disorders. Some of these behavioural treatments include:

Some of the effective treatments for children and adolescents with comorbidity include:

  • Multisystemic therapy
  • Brief strategic family therapy
  • Multidimensional family therapy
  • Motivational interviewing
  • Peer support

Focus on Well-Being and Healthy Living

Striving for healthy living and well-being is part of the treatment process for comorbidities.  The support of family and friends (in school or in the workplace), and participating in sports and other activities that help build self-esteem and strength are vital for the success of the treatment.

A person comforting someone by patting them on the shoulder

Keep In Mind That Help Is Always Available

A lot of people battling comorbid substance use disorder and mental illness don’t get the integrated treatment they need. If you or your loved one is unsure about where to get the right type of care, Freedom from Addiction is here to help in the assessment and treatment of people with concurrent disorders or comorbidities.

For more information about our science-based programs and how we can help work through comorbid conditions, you may contact us. Our team is available 24/7 to attend to your concerns. 


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