5 - Diagnosis and Classification of Substance Use Disorders

Abstract

Systems of diagnosis and classification are essential for effective communication of clinical findings and epidemiological observations. They provide an important basis for the prevention of human disorders and for the management of individuals who develop them. Substance use and misuse exist in a hierarchy. Some forms of substance use are essentially nonharmful or at least low risk, an example being low-level consumption of alcohol. Some substances such as benzodiazepines are prescribed medically for specified disorders. For other substances there is no known level of safe use, for example, tobacco/nicotine and self-injection of any psychoactive drug are liable to cause harm. All these and many other substances have an inherent capacity to cause dependence/addiction, and a range of physical, psychological, and social harms. Over the past few years with the publication of the Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and the Eleventh Revision of the International Classification of Diseases (ICD-11), the terms employed and the definitions of disorders related to substance use, and indeed the very concept of certain disorders, have undergone considerable change. The present chapter presents some of the background knowledge and opinion as to the nature of substance use disorders generated over the past century, and then summarizes and discusses the main diagnostic entities, focusing on DSM-5, ICD-10, and ICD-11, but including DSM-IV for comparison. Most substance use disorders and substance-induced disorders occur as a result of repetitive substance use; one that differs is acute intoxication. Substance Dependence, which was considered to be a central diagnosis in DSM-IV and ICD-10, retains this status in ICD-11 but in DSM-5 has in essence been merged with DSM-IV Substance Abuse to form a new umbrella disorder, termed Substance Use Disorder. “Harmful Substance Use” is an ICD-10 and ICD-11 diagnosis, which denotes repetitive substance use that is causing or has caused physical or psychiatric harm, but where the criteria for Substance Dependence are not fulfilled. The existence of social problems by themselves is insufficient to justify this diagnosis. “Hazardous Substance Use” is a new diagnosis in ICD-11 and denotes repetitive substance use that confers the risk of harm in the future. Addiction has been reincarnated as a descriptive term, for example, “addictive disorders” in DSM-5, and is employed by some medical organizations as a diagnostic term. Separate from these diagnoses are complications such as Substance Withdrawal and numerous Substance-induced Mental Disorders (anxiety disorders, depressive disorders, psychotic disorders), neurocognitive disorders, and substance-induced physical disorders. Diagnosis is based on specific diagnostic criteria that reflect the particular pattern of substance use and the psycho-physiological features 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. 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. However, they may well have clinical diagnostic value with further developments in the years ahead.