Comorbidity: Addiction and Other Mental Illness

Is Drug Addiction a Mental Illness?

Yes, because addiction changes the brain in fundamental ways, disturbing a person’s normal hierarchy of needs and desires and substituting new priorities connected with procuring and using the drug. The resulting compulsive behaviors that override the ability to control impulses despite the consequences are similar to hallmarks of other mental illnesses.

Addiction changes the brain, disturbing the normal hierarchy of needs and desire In fact, the DSM, which is the definitive resource of diagnostic criteria for all mental disorders, includes criteria for drug use disorders, distinguishing between two types: drug abuse and drug dependence. Drug dependence is synonymous with addiction.

By comparison, the criteria for drug abuse hinge on the harmful consequences of repeated use but do not include the compulsive use, tolerance (i.e., needing higher doses to achieve the same effect), or withdrawal (i.e., symptoms that occur when use is stopped) that can be signs of addiction

How Common Are Comorbid Drug Use and Other Mental Disorders?

Many people who regularly abuse drugs are also diagnosed with mental disorders and vice versa. The high prevalence of this comorbidity has been documented in multiple national population surveys since the 1980s. Data show that persons diagnosed with mood or anxiety disorders are about twice as likely to suffer also from a drug use disorder (abuse or dependence) compared with respondents in general. The same is true for those diagnosed with an antisocial syndrome, such as antisocial personality or conduct disorder. Similarly, persons diagnosed with drug disorders are roughly twice as likely to suffer also from mood and anxiety disorders.

”Overlapping Conditions— Shared Vulnerability”).

Gender is also a factor in the specific patterns of observed comorbidities. For example, the overall rates of abuse and dependence for most drugs tend to be higher among males than females. Further, males are more likely to suffer from antisocial personality disorder, while women have higher rates of mood and anxiety disorders, all of which are risk factors for substance abuse.

Why Do Drug Use Disorders Often Co-Occur

With Other Mental Illnesses?

The high prevalence of comorbidity between drug use disorders and other mental illnesses does not mean that one caused the other, even if one appeared first. In fact, establishing causality or directionality is difficult for several reasons. Diagnosis of a mental disorder may not occur until symptoms have progressed to a specified level (per DSM); however, subclinical symptoms may also prompt drug use, and imperfect recollections of when drug use or abuse started can create confusion as to which came first. Still, three scenarios deserve consideration:

1. Drugs of abuse can cause abusers to experience one or more symptoms of another mental illness. The increased risk of psychosis in some marijuana abusers has been offered as evidence for this possibility.

2. Mental illnesses can lead to drug abuse. Individuals with overt, mild, or even subclinical mental disorders may abuse drugs as a form of selfmedication. For example, the use of tobacco products by patients with schizophrenia is believed to lessen the symptoms of the disease and improve cognition.

3. Both drug use disorders and other mental illnesses are caused by overlapping factors such as underlying brain deficits, genetic vulnerabilities, and/or early exposure to stress or trauma. All three scenarios probably contribute, in varying degrees, to how and whether specific comorbidities manifest themselves.

Common Factors Overlapping Genetic Vulnerabilities.

A particularly active area of comorbidity research involves the search for genes that might predispose individuals to develop both addiction and other mental illnesses, or to have a greater risk of a second disorder occurring after the first appears. It is estimated that 40–60 percent of an individual’s vulnerability to addiction is attributable to genetics; most of this vulnerability arises from complex interactions among multiple genes and from genetic interactions with environmental influences. In some instances, a gene product may act directly, as when a protein influences how a person responds to a drug (e.g., whether the drug experience is pleasurable or not) or how long a drug remains in the body. But genes can also act indirectly by altering how an individual responds to stress or by increasing the likelihood of risk-taking and novelty-seeking behaviors, which could influence the development of drug use disorders and other mental illnesses. Several regions of the human genome have been linked to increased risk of both drug use disorders and mental illness, including associations with greater vulnerability to adolescent drug dependence and conduct disorders.

Involvement of Similar Brain Regions.

Some areas of the brain are affected by both drug use disorders and other mental illnesses. For example, the circuits in the brain that use the neurotransmitter dopamine—a chemical that carries messages from one neuron to another—are typically affected by addictive substances and may also be involved in depression, schizophrenia, and other psychiatric disorders.

Indeed, some antidepressants and essentially all antipsychotic medications directly target the regulation of dopamine in this system, whereas others may have indirect effects. Importantly, dopamine pathways have also been implicated in the way in which stress can increase vulnerability to drug addiction. Stress is also a known risk factor for a range of mental disorders and therefore provides one likely common neurobiological link between the disease processes of addiction and those of other mental disorders.

The overlap of brain areas involved in both drug use disorders and other mental illnesses suggests that brain changes stemming from one may affect the other. For example, drug abuse that precedes the first symptoms of a mental illness may produce changes in brain structure and function that kindle an underlying propensity to develop that mental illness. If the mental disorder develops first, associated changes in brain activity may increase the vulnerability to abusing substances by enhancing their positive effects, reducing awareness of their negative effects,or alleviating the unpleasant effects associated with the mental disorder or the medication used to treat it.

The Influence of Developmental Stage Adolescence—A Vulnerable Time.

Although drug abuse and addiction can happen at any time during a person’s life, drug usetypically starts in adolescence, a period when the first signs of mental illness commonly appear. It is therefore not surprising that comorbid disorders can already be seen among youth. Significant changes in the brain occur during adolescence, which may enhance vulnerability to drug use and the development of addiction and other mental disorders. Drugs of abuse affect brain circuits involved in learning and memory, reward, decision making, and behavioral control, all of which are still maturing into early adulthood. Thus, understanding the long-term impact of early drug exposure is a critical area of comorbidity research.

Early Occurrence Increases Later Risk. Strong evidence has emerged showing early drug use to be a risk factor for later substance abuse problems; additional findings suggest that it may also be a risk factor for the later occurrence of other mental illnesses. However, this link is not necessarily a simple one and may hinge upongenetic vulnerability, psychosocial experiences, and/or general environmental influences. A 2005 study highlights this complexity, the high rate of comorbidity between drug abuse and addiction and other mental disorders argues for a comprehensive approach to intervention that identifies and evaluates each disorder concurrently, providing treatment as needed with the finding that frequent marijuana use during adolescence can increase the risk of psychosis in adulthood, but only in individuals who carry a particular gene variant . It is also true that having a mental disorder in childhood or adolescence can increase the risk of later drug abuse problems, as frequently occurs with conduct disorder and untreated attention-deficit hyperactivity disorder (ADHD). This presents a challenge when treating children with ADHD, since effective treatment often involves prescribing stimulant medications with abuse potential. This issue has generated strong interest from the research community, and although the results are not yet conclusive, most studies suggest that ADHD medications do not increase the risk of drug abuse among children with ADHD. Regardless of how comorbidity develops, it is common in youth as well as adults. Given the high prevalence of comorbid mental disorders and their likely adverse impact on substance abuse treatment outcomes, drug abuse programs for adolescents should include screening and, as needed, treatment for comorbid mental disorders.

How Can Comorbidity Be Diagnosed?

The high rate of comorbidity between drug use disorders and other mental illnesses argues for a comprehensive approach to intervention that identifies and evaluates each concurrently, providing treatment as needed. The needed approach calls for broad assessment tools that are less likely to result in a missed diagnosis. Accordingly, patients entering treatment for psychiatric illnesses should also be screened for substance use disorders and vice versa.

Accurate diagnosis is complicated, however, by the similarities between drug-related symptoms such as withdrawal and those of potentially comorbid mental disorders. Thus, when people who abuse drugs enter treatment, it may be necessary to observe them after a period of abstinence in order to distinguish between the effects of substance intoxication or withdrawal and the symptoms of comorbid mental disorders.

This practice would allow for a more accurate diagnosis and more targeted treatment.

How Should Comorbid Conditions Be Treated?

A fundamental principle emerging from scientific research is the need to treat comorbid conditions concurrently—which can be a difficult proposition. Patients who have both a drug use disorder and another mental illness often exhibit symptoms that are more persistent, severe, and resistant to treatment compared with patients who have either disorder alone. Nevertheless, steady progress is being made through research on new and existing treatment options for comorbidity and through health services research on implementation of appropriate screening and treatment within a variety of settings, including criminal justice systems.

Medications

Effective medications exist for treating opioid, alcohol, and nicotine addiction and for alleviating the symptoms of many other mental disorders, yet most have not been well studied in comorbid populations. Some medications may benefit multiple problems. For example, evidence suggests that bupropion (trade names: Wellbutrin, Zyban), approved for treating depression and nicotine dependence, might also help reduce craving and use of the drug methamphetamine. Clearly, more research is needed to fully understand and assess the actions of combined or dually effective medications.

Behavioral Therapies

Behavioral treatment (alone or in combination with medications) is the cornerstone to successful outcomes for many individuals with drug use disorders or other mental illnesses. And while behavior therapies continue to be evaluated for use in comorbid populations, several strategies have shown promise for treating specific comorbid conditions. Most clinicians and researchers agree that broad spectrum diagnosis and concurrent therapy will lead to more positive outcomes for patients with comorbid conditions. Preliminary findings support this notion, but research is needed to identify the most effective therapies (especially studies focused on adolescents)

Examples of Promising Behavioral Therapies for Patients with Comorbid Conditions AdultsTherapeutic Communities (TCs)

TCs focus on the “resocialization” of the individual and use broad-based community programs as active components of treatment. TCs are particularly well suited to deal with criminal justice inmates, individuals with vocational deficits, women who need special protections from harsh social environments, vulnerable or neglected youth, and homeless individuals. In addition, some evidence suggests the utility of incorporating TCs for adolescents who have been in treatment for substance abuse and related problems.

Assertive Community Treatment (ACT)

ACT programs integrate the behavioral treatment of other severe mental disorders, such as schizophrenia, and co-occurring substance use disorders. ACT is differentiated from other forms of case management through factors such as a smaller caseload size, team management, outreach emphasis, a highly individualized approach, and an assertive approach to maintaining contact with patients.

Dialectical Behavior Therapy (DBT)

DBT is designed specifically to reduce self-harm behaviors (such as selfmutilation and suicidal attempts, thoughts, or urges) and drug abuse It is one of the few treatments that is effective for individuals who meet the criteria for borderline personality disorder.

Exposure Therapy

Exposure therapy is a behavioral treatment for some anxiety disorders (phobias, PTSD) that involves repeated exposure to or confrontation with a feared situation, object, traumatic event, or memory. This exposure can be real, visualized, or simulated, and always is contained in a controlled therapeutic environment. The goal is to desensitize patients to the triggering stimuli and help them learn to cope, eventually reducing or even eliminating symptoms. Several studies suggest that exposure therapy may be helpful for individuals with comorbid PTSD and cocaine addiction, although retention in treatment is difficult.

Integrated Group Therapy (IGT)

IGT is a new treatment developed specifically for patients with bipolar disorder and drug addiction, designed to address both problems simultaneously.

AdolescentsMultisystemic Therapy (MST)

MST targets key factors (attitudes, family, peer pressure, school and neighborhood culture) associated with serious antisocial behavior in children and adolescents who abuse drugs.

Brief Strategic Family Therapy (BSFT)

BSFT targets family interactions that are thought to maintain or exacerbate adolescent drug abuse and other cooccurring problem behaviors. These problem behaviors include conduct problems at home and at school, oppositional behavior, delinquency, associating with antisocial peers, aggressive and violent behavior, and risky sexual behaviors.

Cognitive-Behavioral Therapy (CBT)

CBT is designed to modify harmful beliefs and maladaptive behaviors. CBT is the most effective psychotherapy for children and adolescents with anxiety and mood disorders, and also shows strong efficacy for substance abusers. (CBT is also effective for adult populations suffering from drug use disorders and a range of other psychiatric problems.)