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HomeCo-occurring Disorders

Frequently Asked Questions
About Co-occurring Disorders

How many people have co-occurring disorders?

About half of the people treated in mental health settings have had at least one substance use problem in their lifetime, if not within the past year.

About 25 percent to 33 percent of people treated in mental health settings have experienced substance use problems either currently or within the past year.

As many as 50 percent to 75 percent of people in addiction treatment settings also suffer from a current psychiatric disorder.


What are the primary symptoms of co-occurring disorders?

The primary symptoms of co-occurring disorders vary somewhat based upon the specific substance use and psychiatric disorders.

Some typical symptoms of co-occurring disorders do exist, however, and here are several:

  • Using drugs or alcohol to reduce the difficulty or pain associated with the psychiatric problem, and finding out that even if substances worked at first or in the short term, they have not been the solution for the psychiatric problem.
  • The psychiatric problem has generally got worse because of drugs and alcohol.
  • The addiction to alcohol or drugs has generally got worse because of the psychiatric problem.
  • It seems harder to get treatment for both, or harder to benefit from treatment because of having both disorders.
  • It seems harder to find and talk with others who share the same common problem, co-occurring disorders.


What is a substance use disorder?

A substance use disorder refers to both substance abuse and substance dependence (as defined by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision [DSM-IV-TR] published by the American Psychiatric Association) and encompasses the use of both alcohol or other psychoactive substances.

Alcohol abuse (also referred to as alcoholism, alcohol addiction) and drug abuse (drug addiction) is diagnosed when a person's use of a substance persistently interferes with functioning in work or school, social relationships, a medical condition, or when the person uses in dangerous situations.

Alcohol or drug dependence is a more severe condition than alcohol or drug abuse. A person with dependence has failed at attempts to abstain or control his or her use of substances. In some cases, physiological dependence, indicated by tolerance (needing more of a substance to get the same effect) and withdrawal (symptoms occur when the person does stops using the substance) may also exist.


What is a mental health disorder?

A psychiatric disorder or mental health disorder is when someone has problems with their feelings, thinking, functioning, or relationships that are not due to drug or alcohol use, and are not the result of a medical illness.


What is a substance-induced disorder?

Some people develop mental health issues after excessive drinking or other drug use. This may be called a substance-induced disorder. With these disorders, the symptoms of depression, anxiety, or other mental health issues often improve when the person stops using alcohol or other drugs.


How does the use of drugs and alcohol affect a co-occurring mental health problem?

Most people with a mental health problem try substances to feel better. If you are anxious, you may want to try something to make you feel calm; if you are depressed you may want something to make you feel more animated; if you are fearful of others you may want something to make you feel less inhibited and loose; and if you are in psychological pain, you may want something to make you feel numb.

These substance-related solutions, often develop into substance related disorders, and not only fail to repair the mental health problem but also prevent a person from developing real coping skills to have a fulfilling life, satisfying relationships, and feeling comfortable in their own skin.

Illicit drugs and alcohol abuse complicate and compound a mental health problem.


How can chemical use and mental health symptoms interact?

Some symptoms of substance use mimic symptoms of mental disorders. Examples include:

Chemical Symptoms of use Withdrawal symptoms
Alcohol (beer, wine, liquor, moonshine, hooch, booze, vino, sauce) Depression; anxiety Insomnia; anxiety issues; paranoia
Amphetamines (Crank, crystal, ice, speed, Ritalin, Dexedrine; Ecstasy) Possible psychosis; inconsistency in mood; mania; paranoid delusions; anxiety; auditory and visual disturbances; loss of appetite Depression; loss of pleasure; sleep difficulties; paranoia; violent behavior
Cocaine (crack, C, coke, flake, dust, blow, nose candy, rock, white lines) Mania; possible psychosis, hyperactivity Depression; anxiety; loss of pleasure
Cannabis (dope, hemp, weed, ganja, grass, reefer, Mary Jane, hashish, hash, hash oil, chronic, gangster, boom, marijuana, pot, THC) Memory difficulties; depression; lethargy; euphoria; lack of motivation Memory difficulties; lethargy; paranoia
Benzodiazepines (Valium, Ativan, Halcion, Serax, Klonopin, Xanax) Masks anxiety; reduces symptoms of anxiety Concentration difficulties; anxiety; agitation; panic attacks; fear


How does a mental health disorder affect co-occurring addiction and treatment and recovery?

Having a mental health disorder could make a person even more sensitive to the effects of substances. The consequences from excessive use or chronic long-term use happen more rapidly. With the best of intentions, a person with a mental health disorder may try to stop using substances, but after doing so they notice that their psychiatric symptoms return, sometimes more severe. They wonder, "why bother getting clean and sober?"

A mental health disorder complicates and compounds the challenges in overcoming an addiction to drugs or alcohol.


What is the difference between severe and non-severe mental health disorders?

Co-occurring substance use disorders occur in people with severe and non-severe mental health disorders. Severe disorders include schizophrenia, bipolar disorder, schizoaffective disorder, and major depressive disorders. Non-severe mental health disorders include mood disorders, anxiety disorders, adjustment disorders, and personality disorders. Of course, severity can vary substantially within any given diagnostic condition.

For example, depression can be mild, moderate, or severe. PTSD can likewise be well-managed or debilitating. Severity, therefore, is more complex than any specific disorder.

In general, a disorder is diagnosed as "severe" when the patient has many more symptoms than the minimum criteria specify, or some symptoms are especially, severe, or functioning in society or at work is especially compromised.


Why is research on co-occurring disorders challenging?

Researchers have sought to increase our knowledge of the best possible treatments for co-occurring disorders. Because of the complexity and heterogeneity of this field, the research has been cumbersome and slow to progress. One research challenge is in simply defining the term "co-occurring disorder."

For example, a co-occurring disorder may be the co-existence of a diagnosis of schizophrenia and cannabis use, or a diagnosis of alcohol dependence and dysthymia. Further, a person may have had one disorder at one time in his or her life (e.g., alcohol use in college), but not at present, and may suffer at the moment from only one disorder (e.g., major depression). Since experimental rigor is an essential element to research, the need to more precisely define the differences and similarities among co-occurring disorder types has often made the translation of findings to clinical practice exceedingly difficult.

Over the past ten years, both the National Institute on Drug Abuse (NIDA) and the National Institute on Alcohol Abuse and Alcoholism (NIAAA) have increased research support for scientists seeking to develop and test treatments for persons with co-occurring disorders in addiction treatment settings. These institutes each have a different focus with respect to substances used by patients. (NIAAA focuses on alcohol use disorders; NIDA focuses on drug use disorders.)

With the requirement for diagnostic precision in defining research samples, nationally sponsored research has been highly specific in focus. For example, NIDA has funded studies of cocaine-dependent women with PTSD, but these studies have excluded women with PTSD who also have Axis II personality disorders. The NIAAA has funded studies of alcohol-dependent persons with social phobia, but these studies have excluded persons with other substance use or psychiatric disorders. Precise diagnostic combinations and strict inclusion criteria such as these may be important for research (i.e., studies have internal validity) but lack the ability to be extrapolated to real-world settings where patients tend to suffer from a complex mixture of mental health problems and addiction to various substances (i.e., studies need more external or ecological validity).

Pragmatic direction from the field of clinical research, both with respect to studies of medications and psychosocial therapies, have also been difficult for addiction treatment settings to come by. Further, research findings on persons without severe mental illnesses, but who suffer from depression, anxiety, or other "less severe" or disabling conditions have also been slow to accumulate.

Meanwhile, persons with non-severe mental health disorders along with substance use disorders still need professional help. They still need services. Addiction treatment providers and health care professionals struggle with old models of care. They try to provide the best possible treatment so that their patients may have at least an average chance (even though historical research suggests they have a less-than-average chance) at recovery.


Why is the assessment and diagnosis of co-occurring disorders challenging?

Historically, health care professionals who have attempted to treat patients with co-occurring disorders have tried to declare one of the disorders as "primary" and the other as "secondary" based on the order of onset, or some judgment about causality. For instance, if childhood sexual trauma precipitated symptoms of post-traumatic stress disorder (PTSD) and if alcoholism appeared in adulthood, then the perception was that the PTSD must be the primary diagnosis.

Patients were treated first for the primary disorder under the assumption that this treatment would naturally leverage change in the secondary disorder. Generally, with the exception of substance-induced disorders, no evidence for therapeutic efficacy exists for this "primary" or "secondary" approach to treatment.

To complicate diagnosis, a person may have co-occurring disorders even though the mental health disorder and the substance use disorder do not occur simultaneously. For example, a patient may have suffered from a childhood behavioral disorder such as oppositional defiant disorder and now may present with cocaine dependence. Unless this person meets the present criteria for another psychiatric disorder (Axis I or Axis II disorders), he or she may not be assessed as having co-occurring disorders.

Many patients suffer from both substance use and psychiatric disorders, which are chronic (versus transient or acute). Current research shows that a past or recent past diagnosis of a psychiatric or substance use disorder (in the presence of its counterpart) may be sufficient to warrant a co-occurring disorder diagnosis.

A patient may have co-occurring disorders, and yet he or she may not currently exhibit enough symptoms (at the traditional diagnostic threshold) to be diagnosed with both disorders. Using traditional assessments tools, this patient would likely be diagnosed with only one disorder and would not receive adequate treatment for both disorders. This example demonstrates that assessment and diagnosis are important skills for both addiction and mental health clinicians.


What are the basic approaches to treating persons with co-occurring disorders?

Historically, the treatment of co-occurring disorders could be classified into four models, which are listed here in the order they have evolved. The first model (single model) offers the most basic approach to care, while the integrated model offers the most sophisticated.

The four models of care for co-occurring disorders are

  • Single model of care: The "primary" disease and treatment approach
  • Sequential model of care: Treating one disorder at a time
  • Parallel model of care: Concurrent treatment of both disorders (i.e., both disorders are treated at the same time but in different places)
  • Integrated model of care: Treating both disorders (i.e., both disorders are treated at the same time and at the same place, or by the same provider)

Despite the widespread use of the first three models, current research shows that an integrated approach to co-occurring disorder treatment results in the best possible patient outcomes.

Single model of care

Historically, the general assumption among mental health providers was that if an underlying mental health disorder was addressed, such as depression or anxiety, the patient would no longer need to use alcohol or other drugs to cope. Treatment focused on the underlying mental health disorder, with the belief that substance use would "drop off" or return to normal once the underlying disorder was resolved. This approach has been ineffective for substance use disorders and mental health problems.

This model of care is commonly termed the "self- medication" model. This model, at least from a mental health perspective, de-emphasizes the primary disease nature of addiction (substantiated in both human and animal studies), including all the biological and neurological changes associated with long-term substance use. The belief that addiction-related brain changes can be altered by addressing an underlying mental health condition alone is erroneous and without scientific foundation.

Conversely, addiction treatment professionals commonly witness profound if not miraculous changes in mood, anxiety, and self-esteem among patients who received only addiction treatment, including peer recovery group support. Addiction treatment providers often attribute treatment failure to those who drop out of services prematurely or who resist attending peer recovery support group meetings such as AA.

Patients who fare well under this treatment model are those who exhibit symptoms of a mental health disorder but do not have a "full-blown" disorder. For example, an alcoholic patient may suffer from symptoms of depression but not a depressive disorder. Recovery for this patient can be relatively straightforward, and the traditional "addiction-only services" approach for alcoholism is adequate. In contrast, an alcoholic who is clinically depressed may not experience relief from the symptoms of depression simply with abstinence from alcohol. This patient may require a more specific and targeted intervention for the equally severe co-occurring disorder of depression.

Although some patients will benefit from the primary disease and treatment approach , it is likely that those who have diagnosable disorders versus symptoms will require interventions directed at both conditions simultaneously.

Sequential model of care

The sequential treatment model suggests that a primary condition can only be dealt with once the underlying condition is treated so that it becomes less acute or at least less of an interference. For example, an addiction treatment professional may require a patient who is addicted to cocaine to be "stable psychiatrically" before addiction treatment can begin. The definition of stable may range from being "not actively suicidal" to being "capable of tolerating twelve hours of group therapy per day." Alternatively, in a mental health setting, a patient may be required to be "detoxed," or at least not high or intoxicated in order to be included in group therapy or to be seen by a clinician.

Sequential care does not facilitate the simultaneous utilization of both mental health and addiction treatment services. It may or may not conceptualize one of the disorders as primary, but does acknowledge that services may be necessary for both eventually, but not at the same time.

The sequential model essentially requires the patient to "hold off" on receiving services for one disorder while another disorder is the current focus of treatment. This "holding off " period may range from one week (as in, for example, a stay in an alcohol detoxification service) to six months (in residential treatment) to two years (as had been recommended for patients with PTSD who were in early recovery from substance use). In some cases, the sequential approach may be clinically reasonable (e.g., through withdrawal periods) and may help in confirming diagnostic impressions.

Parallel model of care

In this approach, specialty addiction treatment programs concurrently treat persons for addiction while they are in treatment at a mental health agency for a psychiatric disorder. This is known as parallel care or the concurrent model of care. Parallel care happens in addiction treatment programs when addiction treatment services are provided while the patient is also being treated (pharmacologically or in individual psychotherapy) in a mental health setting for a psychiatric disorder. An addiction treatment program may recognize the need for mental health services -- including, but not limited to, psychotropic medication -- and may refer the patient for concurrent psychiatric evaluation and medication management.

Likewise, a mental health professional may refer a psychiatric patient to an addiction treatment center for concurrent treatment for substance use. Parallel services intend to provide care for both mental health and substance use disorders at the same time, but are typically offered in different settings and by different providers. Parallel care can be delivered in consultative, collaborative, or coordinated fashion (see the next question). Parallel services often require the patient to navigate from provider to provider, or from program to program. Sometimes the communication between mental health and addiction providers is poor, and care is fragmented or duplicative or even conflictual. In other instances, parallel models are fairly well organized. Providers work in concert and as a team, even though they are from different programs in different locations. Services offered at the parallel level can approach integration if they are particularly well coordinated and the patient’s experience can be relatively seamless.

Integrated model of care

Integrated treatment may take place at the individual clinician level, the program level, the agency level, or the system of care level.

An integrated clinician is one with developed expertise in both mental health and addictive disorders. Such professionals may have advanced certification in their discipline or mastery in specific treatment approaches.

Integration at the program level happens when members of a treatment team address both mental health and substance use disorders within a single treatment location, episode, record, and experience.

Integration at the agency level may share some, but not all, of the characteristics of programmatic integration, but more navigation by the patient and between clinicians is required. In this instance, an agency may provide both addiction and mental health services but in separate programs or departments. The patient may be asked to meet with two sets of providers, who may vary in clear lines of communication about the treatment plan or the patient’s response to treatment. Integration may also exist at the system level, such as within a geographical region, where clear guidelines and linkages are seamless and formalized. In this instance, two separate agencies may have a well-developed protocol for simultaneously managing patient care. Agencies may share as many as 25 percent of the same patients and have worked out ways to develop a common treatment plan and to monitor patient progress.

Integration requires the active collaboration of both addiction and mental health services providers in the development of a single treatment plan to address both disorders. It also requires the continuing formal interaction and cooperation of these providers in the ongoing reassessment and treatment of the client.


How do treatment/provider relationships vary within models of care?

Models of care may vary by the nature and type of relationship that exists between the addiction and mental health services professionals.

The following terms are used to describe these relationships:

  • Minimal coordination
  • Consultation
  • Collaboration
  • Integration

These terms represent the nature and quality of the relational contact and coordination between service providers. They do not refer to the program structure or location. "Minimal coordination" is the lowest benchmark while "integration" is the highest.

Minimal coordination

A program could be functioning at the level of minimal coordination even though mental health and addiction treatment services are being provided by two people working at the same agency in the same building; whereas, another program could be at the integration level even if services are provided by two people working for different agencies in different programs. In other words, "co-location" guarantees nothing. The relationship may be integrated or minimal regardless of shared space.

Programs at the level of minimal coordination may acknowledge a co-occurring condition; however, there is no effort made to handle the condition. On the rare occasion that a referral is made, the follow-up is typically inadequate.


Programs at the level of consultation may have informal and limited interactions with outside service providers. This may involve transferring medical/clinical information or giving updates on a patient’s progress. The key to this level is that the program attempts to maintain a connection after the initial referral to ensure the referred person enters the recommended treatment service.


Programs at the level of collaboration formally and systematically involve multiple service providers in the sharing of responsibility for treating a person with co-occurring disorders. This includes regular and planned communication, sharing of progress reports, or memoranda of agreement. The key to this level is that all parties involved are aware of their responsibilities and expectations.


Programs at the level of integration involve members of a treatment team working together to cover both mental health and substance use disorders within a single treatment location, episode, record, and experience. Parallel models can approach integration contingent upon the degree of coordination. Some sequential models can also approach integration if the process of linkage is seamless from the clinical and patient perspective. This manual will describe how services can be delivered to support integration, even in parallel or sequential frameworks. How is the treatment of co-occurring disorders improving?

Historically, health care organizations have often failed to approach and treat psychiatric disorders and addiction as concurrent disorders requiring concurrent treatment. In fact, about 50 percent of persons with co-occurring disorders never receive concurrent treatment for both disorders. In cases where concurrent treatment is offered, 75 percent to 85 percent of the time those services are not offered in an integrated manner. This probably leaves less than 15 percent of persons with co-occurring disorders receiving adequate treatment.

Over the past twenty years, increasing efforts have been underway to make positive changes in systems of care. These changes include how, what, and where treatment is delivered, as well as how these services are paid for by third parties such as Medicaid, Medicare, federal block grants, and private insurance companies. Parallel efforts have been occurring even more recently to address workforce issues. In the meantime, current research demonstrates that integrated treatment, which treats both disorders concurrently, offers the best possible outcomes for patients and patients’ families.

An effective, integrated
treatment program


The Co-occurring Disorders Program is the first comprehensive treatment program for people with non-severe mental health disorders that co-occur with substance use disorders. Learn more

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