Mental health and substance abuse meet at a very complicated intersection. From the outside, they may appear very different, but they do not exist in isolation. Many people who struggle with a drug or alcohol problem do so as a way of coping with depression or stress, and consuming harmful substances can severely damage mental health. Some of these relationships occur more frequent than others, and knowing what the most common co-occurring disorders are is very important in understanding how to unravel the catch-22 of addiction and mental health.

What Is a ‘Co-occurring Disorder’?

The term “co-occurring disorder” is used to describe the simultaneous instance of two or more disorders, and it is used in the same manner as “dual diagnosis” or “dual disorder.” All three terms refer to the same problem: a person who has a mental health disorder (such as bipolar disorder) and who also abuses drugs or alcohol. The term “co-occurring disorder” can apply if the patient abuses drugs and alcohol because of their mental distress or if their substance abuse led to the development of a mental health problem.

co-occurring disorders

Psychology Today explains that the two disorders can be of varying severity (even mildness). One disorder may be more present than the other, and the balance may shift from one to the other over time.

Patients who show signs of a co-occurring disorder have more serious symptoms, in terms of length and effects (emotional and social difficulties, for example) than patients who only experience a mental health disorder or an addiction in isolation. Dual diagnosis patients are at risk for both relapsing into their drug or alcohol habit and experiencing a deterioration of their mental health, with one factor affecting the other. This dynamic plays an important role when treating a co-occurring disorder, as patients experiencing both a substance abuse problem and a mental health disorder require specifically designed rehabilitation programs. Such programs are often longer than what patients with a single disorder receive, and progression through dual diagnosis treatment is at a usually slower pace, with more provisions made for relapsing.

The National Alliance on Mental Illness estimates that approximately 50 percent of people who have significant mental health disorders also struggle with addiction to controlled substances. The institute further estimates that 29 percent of all people who have a diagnosis of mental illness abuse alcohol or other drugs.[1]

50 percent of people

who have significant mental health disorders also struggle with addiction to controlled substances.

According to The National Alliance on Mental Illness

Common Co-occurring Disorders

While there do exist common combinations of mental health disorders and substance abuse problems, there is no one-to-one ratio of how a person might develop a dual diagnosis. In answering the question of why people respond differently to the same drugs, Slate put it down to a combination of personality characteristics, genetics, and previous experiences.[2]

Having said that, there are some recurring presentations: major depression and a cocaine addiction, for example, or alcohol addiction with panic disorder or schizophrenia, marijuana addiction with paranoia, or borderline personality disorder with episodes of poly-drug use (the use of multiple drugs in combination to achieve an effect, like counterbalancing the high of a stimulant like cocaine with the drowsiness of a depressant like heroin).[3]

Alcoholism and Antisocial Personality Disorder

One of the more common presentations of a co-occurring disorder is alcoholism and antisocial personality disorder.

Alcoholics are 21 times more likely

to be diagnosed with antisocial personality disorder, as opposed to people who are not alcoholics.

According to The National Institute on Alcohol Abuse and Alcoholism

Antisocial personality disorder is characterized by a destructive and dysfunctional way of thinking. People who have antisocial personality disorder do not care about standards of right and wrong, and they ignore the rights and best interests of others. Mayo Clinic explains that patients can be harshly antagonistic and manipulative, with no regard for the law or their own sense of personal safety. They have no concept of guilt or remorse for their actions, and they will act with sheer impulsivity. It is all but impossible for someone with antisocial personality disorder to maintain a job, a relationship, or academic responsibilities.[4]

According to the National Institute on Alcohol Abuse and Alcoholism, a drinking problem can exacerbate the underlying mental illness, making antisocial behaviors much more prevalent than if there was no alcohol involved. Unfortunately, one of the characteristics of antisocial personality disorder is the patient having a drug or alcohol problem, since they are prone to impulsive, callous behavior.[5]

Another publication by the Institute concluded that patients with the disorder are “more likely to meet the criteria for alcohol abuse or dependence,” and they are more at risk for the well-documented effects of alcohol on aggressive and violent behavioral tendencies. While some research has examined brain function and brain chemistry to explain the cause of aggression induced by alcohol, the Institute cautioned against looking at any one single factor to solve the puzzle. As with most cases of substance abuse and mental health disorders, the full picture is more likely made clear by considering a combination of genetic and environmental components.[6]

Treating antisocial personality disorder can be challenging, because the patient has no sense of perspective or awareness of how their behavior has impacted others. Indeed, the manipulative traits of antisocial personality disorder can manifest in the patient pretending to respond to treatment. The added dimension of alcoholism complicates any kind of therapy, especially when the element of violent behavior puts health care workers and other patients at risk. Court-mandated treatment may be the most effective way of getting a patient to stay in therapy, as the avoidance of incarceration may be too strong an incentive to disregard.[7]

Treatment itself will likely consist of intensive psychoanalysis as an examination of the damage wrought by the patient’s behavior, with a course of medication to treat the effects of the alcohol abuse and moderate aggressive tendencies.[8]

Marijuana and Schizophrenia

Marijuana is often portrayed as being a harmless drug, less dangerous than alcohol, but when used in the presence of an underlying mental health disorder, it can cause severe problems. One such instance of a co-occurring disorder is the presentation of marijuana abuse and schizophrenia.

Harvard Medical School clarified that while marijuana use does not cause schizophrenia, the results of a 2013 study suggest that an “increased familial risk” for the condition was the basis for cannabis users experiencing the effects of schizophrenia.[9]

Schizophrenia is defined as a mental disorder where the patient behaves in socially inappropriate ways and is plagued by hallucinations, diminished social skills, an inability to appropriately express emotions, and an inability to think clearly or logically. Approximately 1.1 percent of the American population (2.5 million people aged 18 or over) is affected, but as many as [10]

40 percent of people with schizophrenia do not receive any treatment in a given year

The American Journal of Psychiatry cites literature on the subject as suggesting that

approximately 50 percent of people with schizophrenia have a co-occurring substance abuse disorder,

usually in relation to alcohol or cannabis (at a rate of three times the general population.)[11]

A November 2014 study of 2,082 people in the journal Medical Psychiatry found a “genetic predisposition” to schizophrenia was associated with increased use of recreational marijuana. The researchers who conducted the study called the finding “significant.”[12] Reporting on the study, The Verge pointed out the relationship between schizophrenia and marijuana may be genetically based, where the same genetic influences that predispose someone to being more likely to use (or abuse) cannabis can also suggest that they may develop schizophrenia, vice versa, or both.

The Verge quotes the lead author of the Molecular Psychiatry study (a genetic psychiatrist at King’s College London) as saying that while the link between people who use marijuana and schizophrenia is well-established, the study finds that people who are at a risk for schizophrenia are more likely to take cannabis and in higher quantities.[13]

The lead researcher of the Harvard Medical School study explained that while cannabis is unlikely to outright cause schizophrenia, it “may have an effect” on when the disorder develops in the person.

Cocaine Addiction and Anxiety Disorders

Cocaine is a powerful drug on its own, but it crosses over alarmingly into the field of mental health. The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders describes 10 psychiatric disorders that can be induced by cocaine.[14]

Some of them include:

  • Delusions (a false belief of paranoia or grandiosity)
  • Psychosis (an inability to distinguish between reality and hallucinations)
  • Tense demeanor and suspicion of any questions
  • Possible homicidal or suicidal thoughts

cocaine use and mental illnessThe Journal of Clinical Psychiatry conducted a literature search and found that paranoia occurs in 68 to 84 percent of patients using cocaine, and violent behaviors as a result of psychiatric symptoms induced by cocaine occur in 55 percent of patients. In patients who commit suicide, cocaine was found in 18 to 22 percent of cases. Many patients who abuse cocaine to the point of becoming dependent on it were also found to have a co-occurring psychiatric disorder.[15]

According to the Journal, cocaine has such an effect that developing a chemical dependence on it is as much a psychiatric and psychological disorder as it is a biological one. Cocaine can produce a wide range of mental illness symptoms, and it can worsen pre-existing mental disorders or lead to the manifestation of mental health disorders that were hitherto dormant or existed only in the potential.

Opioid Addiction and PTSD

Women who abused prescription opioid medications were almost 200% percent more likely to develop PTSD

than men, due to having a “heightened fear response” which statistically makes them twice as likely than men to develop post-traumatic stress disorder.

2014 study published in the American Journal of Drug and Alcohol Abuse

Post-traumatic stress disorder (PTSD) is a mental illness that affects 6.8 percent of adult Americans.[16] It describes a series of stress reactions that affect a patient after they have experienced or seen a traumatic event, and they can last for a lifetime. The symptoms may manifest as a compulsive avoidance of people and places associated with, or even familiar to, the source of the trauma; hyper-arousal, a state of constant tension and fear of an imminent traumatic event; and intrusive thoughts, where the patient experiences recurring flashbacks and nightmares of the initial event, to the point where normal life is disrupted.

The Journal of Addictive Diseases explains that treating the co-occurrence of post-traumatic stress disorder and opioid dependence is a challenge, because the symptoms of PTSD and opioid dependence often intersect. As an example, in the same way that PTSD patients are often hyper vigilant and easily startled, patients who are dependent on opioids often show signs of agitation and distress when they are coming down from their intake or if they are going through withdrawal.[17]

A 2014 study published in the American Journal of Drug and Alcohol Abuse, researchers surveyed 573 people who received treatment for substance abuse. Researchers discovered that study participants who were addicted to prescription opioid medication were 42 percent more likely to develop post-traumatic stress disorder. Patients who combined their prescription opioids with other sedative medications, or even cocaine, put themselves are even higher risks for severe PTSD.[18], [19], [20]

The authors of the study conclude that there is an association between the misuse of opioid medications and the severity of post-traumatic stress disorder symptoms. They advise doctors to be aware of the possibility of PTSD when examining and treating patients with a possibly co-occurring opioid dependency.

The Stress-Vulnerability Model

As with most facets of substance abuse and mental health, genes play a role but only to an extent. Having a genetic predisposition towards a drug or alcohol addiction does not guarantee that a patient will turn to a life of abuse, only that they have a greater chance of doing so, as opposed to someone who has no family history of substance abuse. The same applies to mental health disorders.

One theory to explain why some people develop co-occurring disorders and others do not is the stress-vulnerability model, which puts forward the idea that environmental and biological vulnerabilities collaborate to lead to the development of mental health disorders. The Croatian Psychiatria Danubina journal called the model “extremely useful” in understanding how the relationship between genetics and stress leads to mental illness.[21] [22]

The term “biological vulnerability” refers to the possibility that a patient will develop a mental health condition due to being exposed to triggers early in life (or even pre-natal development, such as contracting a virus while still in utero). They may also inherit predispositions towards such conditions from their parents. “Environmental vulnerabilities” refer to the challenges we face in everyday life, such as financial struggles or relationship difficulties. Put it all together, and the fuse is lit for a co-occurring disorder.

Risk Factors for Co-occurring Disorders

Even then, whether or not that lit fuse leads to an explosion depends on the presence, or lack thereof, of a number of other factors that a patient can, indeed, control (as opposed to any biological or environmental vulnerabilities, over which they may have very limited control). Some of these factors can include:

  • Use of prescription medicine
  • Recreational consumption of drugs and alcohol
  • Social and familial support
  • Coping skills and strategies
  • Hobbies and other pursuits

The right alignment of imbalances in the stress-vulnerability model can be exacerbated by these factors into triggering a co-occurring disorder in a patient. Alcohol and drug use, for example, can be what pushes a patient over the threshold between having a pre-existing biological vulnerability to a mental illness and actually suffering the effects of the illness. Since most people who have co-occurring disorders already have such a vulnerability, even the smallest doses of drugs or alcohol can trigger their mental health disorders.

Stress and Biological Vulnerability

Similarly, stress can increase the biological vulnerability factor by worsening symptoms and causing substance abuse relapses. The National Institute on Alcohol Abuse and Alcoholism explains that brain imaging studies have shown that people who misuse alcohol are motivated to drink because the abuse has caused a dysfunction in how they respond to stress. Simply put, says the Institute, stress increases the risk of alcohol relapse. [23]

It is important to note that while stress is usually associated with negative events (being fired from a job, losing a relationship, being the victim of a crime, etc.), positive events can also put pressure on an individual. Having a baby, for instance, has been cited by 90 percent of couples as the reason for the quality of their relationship declining.[24]

It is also possible that stress can arise from boredom or mental inactivity. When patients with co-occurring disorders have no stimulation, either in their professional or personal lives, their symptoms are worse and they are more prone to using illicit substances to try and inject some excitement and variation in their lives.[25], [26]

The Integrated Treatment Model

Treating a co-occurring disorder presents multiple challenges to a health care practitioner, as they have to focus their efforts on both the substance abuse problem and the underlying mental health issue.

To that end, therapists may employ the integrated treatment model, an approach that emphasizes the similarities between treatment models for mental health and the 12-Step approach for the addiction disorder, and uses them in conjunction to provide the patient with relief from both sides. The integrated treatment model considers both facets of the co-occurring disorder as illnesses, each needing specific, if similar, treatment to address the symptoms and offer healthier and more beneficial ways of thinking.

The integrated model educates the patient regarding their substance abuse and mental health, explaining how the two are related, and how the patient can use this information to deal with the situations that would have previously caused an onset of the mental health disorder or the temptation to self-medicate.[27]

integrated treatment
In explaining the integrated treatment model, the Substance Abuse and Mental Health Services Administration explains how the model works:

  • It helps patients consider the impact of their substance abuse.
  • It involves friends and family in the rehabilitation process.
  • It helps patients establish their own goals and shows them how to work towards those goals.
  • It connects them with jobs and other services that can help them reintegrate into normal life following treatment.
  • It provides specific and special co-occurring disorder counseling.[28]

The integrated treatment model stands as an example of how science and research have made great strides in offering hope and relief to patients and their families. Difficult and painful as though they are, co-occurring disorders do not have to be the end of the road. With the right care and management, anyone can start on the path back to health and happiness.


[1]Living with Co-Occurring Mental & Substance Abuse Disorders.” (October 2013). Psych Central. Accessed May 2, 2015.

[2]Mellow, Paranoid, Happy or Mean?” (June 2014) Slate. Accessed May 2, 2015.

[3]Co-Occurring Disorders.” (November 2014). Psychology Today. Accessed May 1, 2015.

[4]Antisocial Personality Disorder.” (April 2013). Mayo Clinic. Accessed May 2, 2015.

[5]Alcoholism and Co-Occurring Disorders.” (October 1991). National Institute on Alcohol Abuse and Alcoholism. Accessed May 2, 2015.

[6]Antisocial Personality Disorder, Alcohol and Aggression.” (n.d.) National Institute on Alcohol Abuse and Alcoholism. Accessed May 2, 2015.

[7]Antisocial Personality Disorder Treatment.” (October 2013). Psych Central. Accessed May 2, 2015.

[8]Treatment for Antisocial Personality Disorder.” (January 2013). Psych Central. Accessed May 2, 2015.

[9]Harvard: Marijuana Use Doesn’t Cause Schizophrenia.” (December 2013). Psych Central. Accessed May 2, 2015.

[10]Schizophrenia — Fact Sheet.” (n.d.) Treatment Advocacy Center. Accessed May 2, 2015.

[11]Schizophrenia and Co-Occurring Substance Use Disorder.” (March 2007). The American Journal of Psychiatry. Accessed May 2, 2015.

[12]Genetic Predisposition to Schizophrenia Associated with Increased Use of Cannabis.” (November 2014). Molecular Psychiatry. Accessed May 2, 2015.

[13]The Link Between Weed and Schizophrenia is Way More Complicated Than We Thought.” (June 2014). The Verge. Accessed May 2, 2015.

[14]Cocaine-Related Psychiatric Disorders Clinical Presentation.” (October 2013). Medscape. Accessed May 2, 2015.

[15]Cocaine and Psychiatric Symptoms.” (August 1999). The Journal of Clinical Psychiatry. Accessed May 2, 2015.

[16]Epidemiology of PTSD.” (January 2014). U.S. Department of Veterans Affairs. Accessed May 2, 2015.

[17]The Frequency of Agitation Due to Inappropriate Use of Naltrexone in Addicts.” (December 2014). Advanced Biomedical Research. Accessed May 2, 2015.

[18]Co-Occurring Prescription Opioid Use Problems and Post-Traumatic Stress Disorder Symptom Severity.” (July 2014). The American Journal of Drug and Alcohol Abuse. Accessed May 2, 2015.

[19]Posttraumatic Stress Disorder (PTSD).” (n.d.) Anxiety and Depression Association of America. Accessed May 2, 2015.

[20]Sex Differences in Fear Conditioning in Posttraumatic Stress Disorder.” (January 2013). Journal of Psychiatric Research. Accessed May 2, 2015.

[21]The Stress-Vulnerability Model of Co-Occurring Disorders.” (n.d.). Behavioral Health Evolution. Accessed May 2, 2015.

[22]The Stress-Vulnerability Model How Does Stress Impact on Mental Illness At the Level of the Brain and What are the Consequences?” (June 2010). Psychiatria Danubia. Accessed May 2, 2015.

[23]How Does Stress Lead to Risk of Alcohol Relapse?” (n.d.) National Institute on Alcohol Abuse and Alcoholism. Accessed May 2, 2015.

[24]Having Children Adds Stress to Marriage.” (April 2009). US News & World Report. Accessed May 2, 2015.

[25]The Stress of Boredom and Monotony: A Consideration of the Evidence.” (April 1981). Psychosomatic Medicine. Accessed May 2, 2015.

[26]Boredom – A Very Real Road to Addiction.” (April 2013). Psychology Today. Accessed May 2, 2015.

[27]An Integrated Treatment Model for Dual Diagnosis of Psychosis and Addiction.” (October 1989). Hospital & Community Psychiatry. Accessed May 2, 2015.

[28]Integrating Mental Health and Substance Abuse Treatment.” (n.d.) Substance Abuse and Mental Health Services Administration. Accessed May 2, 2015.