Addiction and Other Mental Disorders
Addiction can occur with another mental disorder. Roughly one-half of drug abusers and alcoholics have one or more other mental illnesses. Moreover, of all persons diagnosed with a psychiatric disease, almost one-half have a substance abuse disorder. The substance is most commonly alcohol, followed by marijuana and cocaine. Other commonly abused substances are prescription drugs such as tranquilizers and sleeping pills.
In 2002, approximately four million adults in the United States met the criteria for both a serious mental disorder and substance dependence or abuse the year before. The incidence of abuse is higher among males and those age eighteen to forty-four years. Any of the disorders identified by the American Psychiatric Association’s
Diagnostic and Statistical Manual of Mental Disorders
(DSM-IV) can occur in conjunction with addiction. The dual diagnosis often includes depression, bipolar disorder, schizophrenia, attention deficit hyperactivity disorder (ADHD), generalized anxiety disorder, obsessive-compulsive disorder, post-traumatic stress disorder (PTSD), panic disorder, and antisocial personality disorder.
An impressive body of medical literature documents specific comorbid associations. Subjects with mood or anxiety disorders are two to four times more likely to have a substance use disorder compared with normal subjects. The same is true for people with an antisocial syndrome, such as antisocial personality or conduct disorder. Almost one-half of persons with schizophrenia also have a lifetime history of substance use disorders—a much higher percentage than the one seen in unaffected persons. Cannabis use disorders are prevalent among schizophrenic dual-diagnosis patients, particularly among young adults. In some studies, the rate of smoking in persons with schizophrenia reached 90 percent. The percentage of smokers is also much higher in persons diagnosed with depression, PTSD, and panic disorder, than it is in normal age-matched controls. Methamphetamine use co-occurs with psychiatric manifestations, including depression, suicidal thoughts, and psychosis.
The comorbid associations, however, do not stop at substance use disorders. Studies show that adolescents with Internet addiction have more ADHD symptoms, depression, social phobia, and hostility. Comorbidity of pathological Internet use and psychiatric disorders also is seen in other age groups. Exercise addiction displays a high comorbidity and has many symptoms in common with eating disorders and body image disorders.
Establishing a cause-and-effect relationship for the association of addiction and psychiatric illnesses remains difficult, even when one of these disease categories is diagnosed first. The psychiatric diagnosis often does not happen until symptoms have progressed to a specified level, in accordance with DSM-IV guidelines. Meanwhile, mild symptoms may prompt drug use, and vague recollections of when drug abuse started can generate inaccurate assessments of what occurred first.
The relationship between addiction and other psychiatric disorders is bidirectional. Several mechanisms probably contribute, to different extents, to how specific comorbidities manifest themselves. Because of the substantial economic and psychosocial burden associated with dual diagnosis, identifying the cause of co-occurrence constitutes a public health priority.
Mental Disorders and Addiction
Physicians have long known that psychiatric symptoms such as insomnia, fatigue, depressed mood, and anxiety increase a person’s likelihood of using drugs. It appears the affected person attempts to self-medicate
with drugs, or to engage in other addictive behaviors, to obtain a pleasant feeling (via a neurotransmitter surge in the brain’s reward system). This eases the suffering caused by the underlying illness. Repeated administration of these “remedies” puts the stressed and anhedonic person at risk for addiction, especially when not under adequate medical care.
According to the American Psychiatric Association, persons with schizophrenia use substances such as marijuana to mitigate negative symptoms and some of the adverse effects of antipsychotic medication. Several self-medication mechanisms have been proposed to explain the strong association between schizophrenia and smoking, but none has been confirmed. The use of tobacco products by persons with schizophrenia could alleviate disease symptoms and improve cognition. In addition, smoking behavior also may help patients cope with the social stigma of their disease.
Multiple studies have demonstrated an increased risk for drug use disorders in young persons with untreated ADHD. Some researchers suggest that only ADHD-affected persons with coexisting conduct disorders are vulnerable. Treatment of childhood ADHD with methylphenidate and amphetamines, although efficient in reducing the characteristic manifestations, has generated concern regarding the child’s vulnerability to drug abuse later in life.
New types of addiction are making their way into the lives of psychiatric patients. A number of studies reported excessive online game-playing in persons with major depressive disorder. Depression, hostility, ADHD, and social phobia were found to predict the occurrence of Internet addiction in follow-up studies. Hostility and ADHD represented the most important predictors of Internet addiction in male and female adolescents, respectively.
Mental Disorders and Drugs of Abuse
Substances of abuse, and the expanding cycle of brain dysfunction they produce, can cause users to experience symptoms of mental illness in the absence of a previous psychiatric history. Ecstasy (MDMA) use, for example, causes long-term deficits in brain serotonin function, resulting in depression and anxiety. Psychosis occurs in stimulant abusers (for example, in the chronic phase of amphetamine use), apparently because of alterations in the dopamine system. Stimulants also cause anxiety, panic attacks, and sleep disorders.
Suicidal behavior is frequently observed among cocaine-dependent persons. Cocaine affects mood negatively, as indicated by the high frequency of dysphoria (unpleasant mood) in users. Brain imaging and postmortem studies conducted in these subjects show reductions in dopamine receptors and in dopamine release. Dopamine is a key molecule in reward and motivational circuits; therefore, these reductions could lead to loss of interest and depressed mood. In persons with predisposing factors, this effect elevates the risk for suicide.
Elucidating the long-term impact of early drug exposure is an important area of comorbidity research. Chronic drug abuse by teenagers represents a major concern because, at this formative stage, it has a negative impact on socialization and cognitive development and can contribute to the generation of mental disorders. The connection between early drug exposure and psychopathology is, however, a complex one, because of potential genetic and environmental influences. One study, for example, shows that frequent marijuana use in adolescence increases the risk of psychosis in adulthood, but only in subjects with a certain gene variant.
Overlapping Causes
Addiction and other psychiatric illnesses have overlapping causes that include genetic vulnerabilities, brain dysfunction, and early exposure to stress or trauma. Research is aimed at finding genes that favor the development of both addictive behavior and mental diseases, or increase the risk of comorbidity. Approximately one-half of a person’s vulnerability to addiction is caused by genetics, mainly through complex relationships between genes and interactions with environmental factors.
Several regions of the human genome have been linked to an elevated risk of both substance use disorders and mental illness. One prominent example is the existence of genetic factors associated with a higher vulnerability to teenage drug dependence and conduct disorders. Pathological gambling shares genetic vulnerability factors with antisocial behaviors, alcohol dependence, and major depression.
Pathological changes in certain brain areas and neurotransmitter systems underlie both substance use disorders and other mental illnesses. This led to the hypothesis that brain changes associated with one disease category may influence the other. Drug abuse may cause structural changes in the brain that render a person more prone to developing a psychiatric disorder. When a mental disorder develops first, it changes brain activity in a way that increases the propensity to abuse substances in an attempt to alleviate the unpleasant effects of the mental disorder or the medication used to treat it.
Dopaminergic and serotonergic dysfunctions lead to psychiatric disorders and increase the risk for addiction. Dopaminergic circuitry, for example, is altered both in addiction and in psychiatric disorders, such as depression and schizophrenia. The presence of these abnormalities may predispose a person to developing schizophrenia, increase the rewarding effects of substances like nicotine, and even diminish the person’s ability to quit smoking. The drug clozapine is used to treat schizophrenia and acts on nicotine receptors, among others. It improves attention and memory in animal models of schizophrenia, and it reduces smoking in persons with schizophrenia. This observation further underscores the existence of common disorder mechanisms.
Psychosocial stress participates in the initiation and maintenance of addictive disorders and other psychiatric diseases, including depression and PTSD. Evidence suggests that the limbic-hypothalamic-pituitary-adrenal axis, which controls stress reactions, may be important in the development of depression and addictive disorders. Dopamine signaling has also been implicated in the way stress increases vulnerability to drug addiction. As stress is a risk factor for multiple mental disorders, these findings provide a possible link between the mechanisms underlying addiction and those of other psychiatric disorders.
Diagnosis and Treatment of Comorbidity
The strikingly high rate of addiction and psychiatric illness co-occurrence calls for a thorough evaluation of patients and prompt, concurrent treatment of these disorders. Patients presenting with mental illnesses should receive screening for addictions, and substance abusers should undergo a comprehensive psychiatric evaluation. This approach will help patients with dual diagnosis, in which symptoms may be more severe and difficult to manage than in patients with only one disorder.
Substance abuse in persons with schizophrenia, for example, is associated with poorer clinical outcomes and contributes significantly to their morbidity and mortality. Skilled assistance and careful observation will also distinguish between the symptoms of intoxication or withdrawal and the often similar manifestations of comorbid mental disorders.
Health providers should be aware that the rates of addiction relapse are higher in people with psychiatric comorbidities. Smokers with depression, for example, have a more difficult time quitting and require more attempts to quit than do smokers without depression.
Targeted and early treatment can significantly reduce the increased risk of persons with mood disorders resorting to drugs and can reduce the development of severe mental illnesses in persons with addictive behaviors. In the United States, the care for patients with comorbidity poses several problems. The health system employs distinct channels for treating psychiatric disorders and addiction. Health practitioners’ qualifications render each system better suited to dealing with one or the other of these disease categories. When faced with dual-diagnosis patients, substance-abuse treatment centers may be reluctant to use medications, even when needed to treat mental disorders. Some may not have employees qualified to prescribe and monitor medication. Consequently, when surveyed, patients with comorbidities report the lowest satisfaction with health care and the greatest prevalence of unmet need.
Patient population factors (such as social status, gender, and scope of insurance coverage) contribute to a deepening of the gap between the two closely related therapeutic fields. According to the National Institute on Drug Abuse, when suffering from both substance abuse and mental illness, women tend to seek help from mental health practitioners, whereas men prefer substance-abuse treatment channels. Epidemiological studies indicate that one-half of military veterans diagnosed with PTSD have a substance use disorder comorbidity, which creates a challenge for the health system. Urgent research efforts are needed to identify the best treatment strategies for addressing PTSD-substance abuse comorbidities and to explore possible distinct treatments for combat versus civilian PTSD.
A high percentage of detainees in prisons and jails have a psychiatric disorder associated with substance abuse or addiction. In these settings, comorbidity treatment avenues are insufficient and improvements have a great potential to enhance public health and safety.
Despite these difficulties, progress in screening and treatment of comorbidities has been made in many settings. Research efforts aim to identify the best pharmacologic treatments that reduce cravings, while alleviating associated mental disorders. One successful approach concerns patients who receive atypical antipsychotic agents, especially clozapine: They smoke less and have an easier time quitting. Psychosocial strategies that show promise in treating comorbidity include cognitive-behavioral therapy, therapeutic communities, assertive community treatment, and integrated group therapy.
Bibliography
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