Is there a relationship between childhood ADHD and later drug abuse? See page 2. from the director: Comorbidity is a topic that our stakeholders––patients, family members, health care professionals, and others–– frequently ask about. It is also a topic about Comorbidity: which we have insufficient information, so it remains a research priority for Addiction and Other Mental Illnesses NIDA. This Research Report provides information on the state of the science in this area. Although a variety of diseases commonly co-occur with drug abuse and addiction (e.g., HIV, hepatitis C, cancer, cardiovascular disease), this report focuses only on the comorbidity of drug use disorders and other mental illnesses.* To help explain this comorbidity, we need to first recognize that drug addiction is a mental illness. It is a complex brain disease characterized by compulsive, at times uncontrollable drug craving, seeking, and use despite devastating consequences— behaviors that stem from drug-induced changes in brain structure and function. These changes occur in some of the same brain areas that are disrupted in other mental disorders, such as depression, anxiety, or schizophrenia. It is therefore not surprising that population surveys show a high rate of co-occurrence, or comorbidity, between drug addiction and other mental illnesses. While we cannot always prove a What Is connection or causality, we do know that certain mental disorders are established Comorbidity? risk factors for subsequent drug abuse— and vice versa. It is often difficult to disentangle the hen two disorders or illnesses occur in the same overlapping symptoms of drug addiction and other mental illnesses, making person, simultaneously or sequentially, they diagnosis and treatment complex. Correct diagnosis is critical to ensuring appropriate are described as comorbid. Comorbidity also and effective treatment. Ignorance of or W implies interactions between the illnesses that affect the failure to treat a comorbid disorder can jeopardize a patient’s chance of recovery. course and prognosis of both. We hope that our enhanced understanding continued inside of the common genetic, environmental, and neural bases of these disorders—and the dissemination of this information—will lead to improved treatments for comorbidity and *Since the focus of this report is on comorbid drug use disorders and will diminish the social stigma that makes other mental illnesses, the terms “mental illness” and “mental disorders” patients reluctant to seek the treatment will refer here to disorders other than substance use disorders, such as they need. depression, schizophrenia, anxiety, and mania. The terms “dual diagnosis,” Nora D. Volkow, M.D. “mentally ill chemical abuser,” and “co-occurrence” are also used to refer to Director drug use disorders that are comorbid with other mental illnesses. National Institute on Drug Abuse Research Report Series Comorbidity Is Drug Addiction How Common a Mental Illness? Are Comorbid Yes, because addiction changes Drug Use and the brain in fundamental ways, Other Mental disturbing a person’s normal Disorders? hierarchy of needs and desires and substituting new priorities Many people who regularly Childhood ADHD connected with procuring and abuse drugs are also diagnosed and Later Drug using the drug. The resulting with mental disorders and vice compulsive behaviors that versa. The high prevalence of this Problems override the ability to control comorbidity has been documented impulses despite the consequences in multiple national population Numerous studies have are similar to hallmarks of other surveys since the 1980s. Data documented an increased risk for mental illnesses. show that persons diagnosed drug use disorders in youth with with mood or anxiety disorders untreated ADHD, although some In fact, the DSM, which is the suggest that only a subset of definitive resource of diagnostic are about twice as likely to suffer these individuals are vulnerable: criteria for all mental disorders, also from a drug use disorder those with comorbid conduct (abuse or dependence) compared disorders. Given this linkage, it is with respondents in general. The important to determine whether Addiction same is true for those diagnosed effective treatment of ADHD changes the with an antisocial syndrome, could prevent subsequent drug brain, disturbing such as antisocial personality abuse and associated behavioral or conduct disorder. Similarly, problems. Treatment of childhood the normal persons diagnosed with drug ADHD with stimulant medications hierarchy of disorders are roughly twice as such as methylphenidate or needs and amphetamine reduces the likely to suffer also from mood impulsive behavior, fidgeting, desires. and anxiety disorders (see page 3, and inability to concentrate “Overlapping Conditions— Shared that characterize ADHD. Yet, Vulnerability”). some physicians and parents includes criteria for drug use Gender is also a factor in the have expressed concern that disorders, distinguishing between specific patterns of observed treating childhood ADHD with two types: drug abuse and drug comorbidities. For example, stimulants might increase a child’s Drug dependence the overall rates of abuse and vulnerability to drug abuse later in dependence. dependence for most drugs tend life. Recent reviews of long-term is synonymous with addiction. studies of children with ADHD By comparison, the criteria for to be higher among males than who were treated with stimulant drug abuse hinge on the harmful females. Further, males are more medications (e.g., Adderal, Ritalin, consequences of repeated use but likely to suffer from antisocial Concerta) found no evidence for do not include the compulsive personality disorder, while women this increase. However, most of use, tolerance (i.e., needing higher have higher rates of mood and these studies have methodological doses to achieve the same effect), anxiety disorders, all of which are limitations, including small sample or withdrawal (i.e., symptoms that risk factors for substance abuse. sizes and nonrandomized study designs, indicating that more occur when use is stopped) that research is needed, particularly can be signs of addiction. with adolescents. 2 NIDA Research Report Series Overlapping Conditions—Shared Vulnerability High Prevalence of Drug Abuse and Dependence Why Do Drug Use Among Individuals With Mood and Anxiety Disorders Disorders Often Co- 25 Occur With Other All respondents 20 Any mood disorder Mental Illnesses? Any anxiety disorder The high prevalence of comorbidity 15 between drug use disorders and other mental illnesses does not mean that one 10 caused the other, even if one appeared Because mood disorders first. In fact, establishing causality or 5 increase vulnerability to directionality is difficult for several drug abuse and addiction, reasons. Diagnosis of a mental disorder the diagnosis and 0% may not occur until symptoms have Any Drug Opioids Amphetamines Cocaine Marijuana treatment of the mood disorder can reduce the progressed to a specified level (per Higher Prevalence of Mental Disorders risk of subsequent drug DSM); however, subclinical symptoms Among Patients With Drug Use Disorders use. Because the inverse may also prompt drug use, and may also be true, the imperfect recollections of when drug use 50 diagnosis and treatment or abuse started can create confusion as of drug use disorders to which came first. Still, three scenarios All respondents may reduce the risk of 40 Any drug use disorder developing other mental deserve consideration: illnesses and, if they do 1. Drugs of abuse can cause abusers to occur, lessen their severity 30 experience one or more symptoms of or make them more another mental illness. The increased amenable to effective risk of psychosis in some marijuana 20 treatment. Finally, because more than 40 abusers has been offered as evidence percent of the cigarettes for this possibility. 10 smoked in this country are smoked by individuals 2. Mental illnesses can lead to drug with a psychiatric disorder, abuse. Individuals with overt, mild, 0% Mood Disorders Anxiety Disorders such as major depressive or even subclinical mental disorders disorder, alcoholism, post- may abuse drugs as a form of self- traumatic stress disorder medication. For example, the use (PTSD), schizophrenia, or Higher Prevalence of Smoking Among of tobacco products by patients Patients With Mental Disorders bipolar disorder, smoking by patients with mental with schizophrenia is believed to 80 illness contributes lessen the symptoms of the disease Current smokers greatly to their increased and improve cognition (see page 70 morbidity and mortality. 4, “Smoking and Schizophrenia: 60 Self-Medication or Shared Brain 50 Circuitry?”). 40 3. Both drug use disorders and 30 other mental illnesses are caused by overlapping factors such as 20 underlying brain deficits, genetic 10 vulnerabilities, and/or early exposure 0% to stress or trauma. No Mental Major Alcohol Post-Traumatic Drug Bipolar Illness Depression Abuse or Stress Abuse or Disorder Dependence Disorder Dependence All three scenarios probably contribute, in varying degrees, to how and whether specific comorbidities manifest Data in top two graphs reprinted from the National Epidemiologic Survey on Alcohol and Related Conditions (Conway et al., 2006). Data in bottom graph from the 1989 U.S. National Health Interview Survey (Lasser et al., 2000). themselves. NIDA Research Report Series 3 Common Factors Overlapping Genetic Vulnera- bilities. A particularly active