The prevalence of alcohol and drug disorders in primary care outpatients is between 23% and 37%. The cost to society of these disorders is staggering. Each year in the United States substance use disorders are associated with 100,000 deaths and costs of approximately $100 billion. The high prevalence of these disorders in primary care outpatients suggests that family physicians are confronted with these problems daily. However, these disorders rarely present overtly. Patients in denial about the connection between their substance use and the consequences caused by it frequently minimize the amount of their use and often do not seek assistance for their substance use problem.

The epidemiology of alcohol and drug disorders has been well studied and is most often reported from data of the National Institute of Mental Health Epidemiologic Catchment Area Program (ECA). Lifetime prevalence rates for alcohol disorders from the ECA survey data were 13.5%. For men, the lifetime prevalence was found to be 23.8%, and for women, 4.7%. The National Comorbidity Survey revealed lifetime prevalence of alcohol abuse without dependence to be 12.5% for men and 6.4% for women. For alcohol dependence, the lifetime prevalence was 20.1% in men and 8.2% in women. The ECA data yield an overall prevalence of drug use disorders of 6.2%. As with alcohol use disorders, drug use disorders occur more frequently in men (lifetime prevalence 7.7%) than in women (4.8%). Characteristics known to influence the epidemiology of substance use disorders include gender, age, race, family history, marital status, employment status, and educational status.

The difference between abuse and dependence is an important one. With substance abuse, patients retain control of their use. This control may be affected by poor judgment and social and environmental factors, and mitigated by the consequences of the patient’s use. Patients who become dependent (addicted) no longer have full control of their drug use. The brain has been “hijacked” by a substance that affects the mechanism of control over the use of that substance. This addiction is far more than physical dependence. The need to use the drug becomes as powerful as the drives of thirst and hunger. Evidence that the brains of addicted individuals are different from those of nonaddicted persons is enormous. Many of these abnormalities predate the use of the substance and are thought to be inherited. In genetically predisposed individuals, substances of abuse cause changes in the dopaminergic mesolimbic system that result in a loss of control over substance use. These changes are mediated by several neurotransmitters: dopamine, γ-aminobutyric acid (GABA), glutamate, serotonin, and endorphins. The different classes of substances of abuse act through one or more of these neurotransmitters, ultimately affecting the level of dopamine in the mesolimbic system (otherwise known as the reward pathway). These changes in the brain are permanent and are the primary reason for relapse in the addicted patient trying to maintain abstinence or control of use.

Although neurobiology plays a large role in addiction, the precursors of substance abuse are also environmental and include family, school, community, and peer factors (Table 56-1). These multiple factors make the design of effective prevention very difficult. Primary prevention is designed to prevent the use of substances, thereby making abuse impossible. These programs are designed primarily for the young. Secondary prevention consists of screening programs to identify abuse early and to redirect the patient’s behavior before addiction becomes overt. In tertiary prevention, the focus is on the treatment of addictive behavior in an effort to prevent the consequences of compulsive use. Prevention programs can be divided into those that address the four environmental areas of risk: family, school, peers, and community. Family physicians can support these efforts by including the following behaviors in their practice:

• Supporting efforts to strengthen parenting skills, family support, and communication.
  
• Providing patient and community education about drug and alcohol use, abuse, and treatment.
  
• Screening and assessing patients of all ages for substance use disorders in the office and hospital.
  
• Supporting community efforts in substance abuse prevention.
  
• Endorsing and promoting public policy that supports prevention, early detection, and treatment of substance use disorders.

Symptoms and Signs

The signs and symptoms of substance abuse are varied and often subtle. This is complicated by the fact that most patients do not recognize their substance use as the cause of their problems and are often quite resistant to that interpretation. Consequently, the family physician must have a high index of suspicion, recognizing that the prevalence of substance use disorders in outpatient primary care is high. A perspective that recognizes the prevalence of these disorders will enable physicians to interpret potential clues to substance use (Table 56-2).

The diagnosis of substance abuse or dependence is made primarily on the basis of a careful history. However, substance-disordered patients may be deliberately less than truthful in their history, and often the patient’s denial prevents the physician from seeing the connection between substance use and its consequences. Signs of sedative hypnotic or alcohol withdrawal may be misinterpreted as an anxiety disorder. Chronic use of stimulants may present as a psychotic disorder. In fact, in the face of active substance abuse, other psychiatric diagnoses often must wait for detoxification before they can be accurately assessed.

Screening Measures

The diagnosis of substance use disorders is most typically begun with a screening test that identifies a user at risk. The CAGE (Cut down, Annoyed, Guilty, and Eye opener) questionnaire (Table 56-3) is perhaps the most widely used screening tool for the identification of patients at risk for substance use disorders. When a patient answers yes to two or more questions of the CAGE, the sensitivity is 60%-90% and the specificity 40%-60% for substance use disorders. Because a screening test is more predictive when applied to a population more likely to have a disease, clinical clues to substance use disorders may be useful indicators to determine who to screen (see Table 56-2).

Methods to Differentiate Abuse from Dependence

Diagnostic Criteria

Once a patient with a substance use problem is identified, it becomes necessary to determine whether the disorder involves abuse or dependence. Substance abuse is a pattern of misuse during which the patient maintains control, whereas in substance dependence, control over use is lost. Physiologic dependence, evidenced by a withdrawal syndrome, may exist in either state. The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) diagnostic criteria for substance abuse and dependence are listed in Tables 56-4 and 56-5.

Withdrawal Syndromes

Although not always seen with substance abuse, physiologic dependence suggests abuse unless the patient is on long-term prescribed addictive medicines. Table 56-6 contrasts signs and symptoms of withdrawal from alcohol and other sedative-hypnotic drugs, opiates, and cocaine and other stimulant drugs. Alcohol withdrawal may be life threatening, if not properly treated. Opiate withdrawal is not life threatening and neither is withdrawal from cocaine or other stimulants, although they both may be associated with morbidity and relapse to substance abuse.

In dealing with sedative-hypnotic, alcohol, or opiate withdrawal, assessment of the degree of withdrawal is important to determine appropriate use and dose of medication to reduce symptoms and, in the case of sedative hypnotic drugs or alcohol, prevent seizures and mortality. The Clinical Institute Withdrawal Assessment of Alcohol Scale, Revised (CIWA-AR) allows quantification of the signs and symptoms of withdrawal in a predictable fashion that allows clinicians to discuss the severity of withdrawal for a given patient and thus choose intervention strategies that are effective and safe. This tool is available online and can be downloaded from the American Society of Addiction Medicine (ASAM) web site (http://asam.org).

Laboratory Findings

Biochemical markers may help support the diagnostic criteria gathered in the history, or can be used as a screening mechanism to consider patients for further evaluation (Table 56-7).