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Substance use disorders (SUDs) can be immensely complicated all on their own. But according to statistics, between 57% to 84% of people with a substance use disorder struggle with a co-morbidity. Also called a dual diagnosis or a co-occurring disorder, these conditions take place alongside an existing addiction or dependence.

A co-occurring condition can immensely complicate the diagnosis and treatment of SUDs because many of their symptoms appear similar. But more than that, these conditions can also exacerbate one another, feeding into each others’ mechanism and pathophysiology so that one worsens as the other progresses.

What Causes Co-Occurring Disorders?

According to statistics, comorbidities for addiction can be unfortunately common. Recent numbers show that 7.9 million adults in the United States suffered from co-occurring diseases in the year 2014. Most co-occurring disorders that come hand in hand with addiction are mental disorders. The reason for this is because addiction is a mental health disease, which means their mechanisms often work through similar pathways. Based on research findings, comorbidities tend to exist prior to the development of a substance use disorder. Another interesting fact is that as substance use progresses into addiction and dependence, comorbidities tend to increase in severity. That’s not to say however that mental health disorders can’t develop as a result of substance abuse. In some individuals, continued use of illicit substances can alter brain function and lead to the development of comorbidities. While it’s not entirely clear how these conditions feed off of one another, some experts speculate that there may be three likely reasons for comorbidities to develop especially within the context of mental health and drug abuse:

  • Similar Risk Factors – SUDs and various mental health disorders often overlap in terms of risk factors. For instance, both depression and SUD list unemployment, poor family relationships, and poverty as risk factors. Since these conditions are the same between both conditions, the individual becomes more likely to develop both.
  • Drug Induced Changes in the Brain – Drug use can induce changes in both brain chemistry and even anatomy. These changes can affect a person’s mood, personality, impulses, motivation, and drive, thus impacting the way they think and act.

As the changes progress further, they may start to show signs of mental health disorders. For instance, some individuals are diagnosed with methamphetamine-induced psychosis which is characterized by schizophrenia-like symptoms that result from methamphetamine abuse.

  • Self-Medication – Individuals struggling with the symptoms of mental health disorders may want to seek any way to relieve the discomfort, distress, and pain. Many of them find that comfort in the use of illicit substances which can temporarily mask the symptoms, but the effects are only short lived.

Another tragic truth about ‘self-medicating’ is that although the substance might make the individual feel better for a time, the long-term effects may significantly increase the severity of the mental disorder. That means that as the addiction progresses, the episodes of the disorder may become even more pronounced.

Common Co-Occurring Disorders

Addiction can come with any number of comorbidities, but some are more common than others. These include:


More than 264 million people worldwide suffer from depression. Characterized by a depressed mood, this mental health condition can reduce motivation and impose feelings of worthlessness and hopelessness. People suffering from severe depression may battle with suicidal thoughts associated with a negative self-concept or traumatic past experiences. Some people who struggle with depression turn to illicit substances and alcohol to escape negative emotions. The high can temporarily subdue negative ideas about the self, suicidal thoughts, and feelings of shame and guilt. But as the effects of the drug subside, the person is left feeling worse than before. Thus, it becomes a vicious cycle of depression feeding drug abuse and vice versa.


Characterized by delusions and hallucinations, schizophrenia is a mental health disorder that causes an individual to lose touch with reality. Individuals with this disorder may take illicit substances to manage their psychotic symptoms. However there are others who may take drugs as a result of delusions or hallucinations. For instance, some individuals may hear voices telling them to engage in certain activities, while others hold on to false beliefs that compel them to take drugs. Unfortunately, individuals with schizophrenia have severe chemical imbalances in their brain that may be intensely impaired by the use of drugs. As they become more and more addicted to illicit substances, the frequency and severity of psychotic episodes increases significantly.


Another common mental health condition, anxiety occurs when a person feels intrusive, persistent worry or apprehension when faced with certain situations. A common form of anxiety is social anxiety disorder which is characterized by unreasonable feelings of unease, stress, and fear when faced with social situations. In order to overcome the overwhelming feelings of dread and anxiety, individuals suffering from this condition may take illicit substances to subdue the negative feelings. As they develop a dependence, they may no longer be able to handle their anxiety without the use of drugs. This puts them at risk of severe addiction in order to function within society.

Bipolar Disorder

When a major depressive episode occurs with episodes of mania, then the person may be diagnosed with bipolar disorder. This condition is characterized by severe changes in mood, with the person feeling marked depression for a time and then cycling to a manic episode where they might be grandiose, uninhibited, and violent. Some studies have found that individuals suffering from bipolar disorder will suffer from substance use disorder at some point in their lives. Although the reason for the link isn’t clear, experts speculate that the loss of inhibitions during the manic phase might be partly to blame for the development of an addiction.

Post-Traumatic Stress Disorder

When an individual experiences a significant traumatic experience — like seeing someone die a violent death, being the victim of a crime, or even being deployed in active military service — they may develop post-traumatic stress disorder. This condition is manifested by flashbacks and intrusive memories associated with the traumatic event. When these memories are triggered, the person may feel like they’re reliving the experience all over again, resulting in panic attacks, anxiety, depression, among other things. Because the memories can be just as painful and frightening as the experience itself, some people who struggle with PTSD use drugs to cover up the trauma. Many of those who use alcohol or illicit substances to cope with PTSD develop long term addictions since their substance use can’t resolve the trauma in the first place.

Eating Disorders

Individuals with eating disorders often struggle with their body image. With an intense fear of gaining weight, individuals suffering from eating disorders deprive themselves of food in an effort to lose and to prevent gaining weight. For some of those with eating disorders, simply refusing to eat may not be sufficient to satisfy their desires. In this case, sufferers take drugs in order to speed up their weight loss. Naturally, they shed pounds much faster with the help of illicit substances and alcohol. But with their bodies severely deprived of necessary nutrition — and pumped with harmful substances — they’re put at risk of overdose and death.

Human Immunodeficiency Virus

Otherwise called HIV, this condition isn’t a mental health disorder but is worthy of mention nonetheless. According to studies, of 15.9 million who inject illicit substances, 3 million are infected with HIV. That’s because the virus can be spread through contaminated needles which are commonly shared with drug users throughout the urban poor. An individual who takes illicit substances reduces the body’s ability to combat HIV. Studies have found that drug use can increase the viral load and accelerate the progression of the disease. Unfortunately, there is no cure for HIV however sobriety might help to improve a patient’s prognosis.

The Dual Diagnosis – A Double Whammy

Treating addictions with co-occurring disorders can be far more complicated than treating the addiction alone. What many don’t realize however is that it’s rare that you’ll find an individual without even just a mild mental health disorder hand in hand with a substance use disorder. Fortunately, there are numerous stories of individuals successfully achieving sobriety against all the odds. As with addiction, the best way to resolve a comorbid disorder would be to nip the problem at the root. Unearthing past traumas, resolving the effects of abuse, and restoring family relationships are just some of the ways to undo mental health disorders all together. And while it might be a long and tedious process, the rewards of sobriety and mental wellness are well worth the struggle.

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