Diagnosis and Classification of Substance Use Disorders

Abstract

Substance use and misuse exist at a hierarchy of disorders. Some forms of substance use, e.g., alcohol, are non-harmful or at least very low risk, while others, such as the prescription of benzodiazepines, are medically appropriate in certain circumstances. However, alcohol, certain prescribed (and pharmacy) medications, and illicit drugs have an inherent capacity to cause dependence (addiction) and a range of physical, psychological, and social harms. A hierarchy of diagnoses exists to describe various levels of substance use disorders. Repetitive substance use, which confers the risk of harmful consequences because of its known effects, is termed “hazardous use” or “risky use”. These terms are used widely by many national authorities and medical and health care organizations. “Substance abuse” is a Diagnostic and Statistical Manual of Mental Disorders, 4th Edition term denoting a maladaptive and repetitive pattern of substance use that causes essentially social and personal problems. “Harmful use” is an International Statistical Classification of Diseases and Related Health Problems, 10th Revision term denoting repetitive substance use that actually causes physical or psychiatric harm. The existence of social problems is in itself insufficient for the diagnosis of harmful use. At the top of the hierarchy in both the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition and the International Statistical Classification of Diseases and Related Health Problems, 10th Revision is a substance dependence syndrome defined as a psychobiological syndrome that comprises impaired control over substance use, tolerance, and withdrawal symptoms and is characterized by continued use of the substance despite harmful consequences. The term “dependence syndrome” has replaced older terms such as “alcoholism” and “addiction”, although there is a move presently to reinstate addiction as a diagnostic term. Underlying the dependence syndrome is a set of profound and enduring neurobiological changes in the reward, stress, and control systems in the midbrain and lower forebrain. I liken the dependence syndrome to a powerful internal “driving force” that drives the person’s use of that substance in a self-perpetuating way. Separate from these diagnoses, which refer to repeated substance use and are the “core” substance use disorders, are the numerous complications, including substance-induced mood disorders, anxiety disorders, psychotic disorders, and many neuropsychiatric impairments and physical diseases. Diagnosis is based on a set of specific diagnostic criteria that reflect the particular pattern of substance use and the psycho-physiological attributes and mental and other consequences of the condition. Clinical diagnosis of these disorders is based on clinical knowledge and training, and there are several diagnostic interview schedules, together with screening and assessment instruments, that contribute to the diagnosis. Schedules quantifying various forms of substance use also are available; laboratory tests reflecting the physiological effects of alcohol or that detect the presence of a drug or its metabolites also contribute to the diagnosis but do not specifically indicate which one. Cerebral imaging techniques are increasingly powerful demonstrations of the physiological processes of dependence but are not yet at the stage where they can contribute directly to making a diagnosis. The same applies to various genetic and other physiological tests. However, these may well have clinical diagnostic value with their further development in the years ahead.