01 - Introduction

Introduction

The Maudsley® Prescribing Guidelines in Psychiatry, Fifteenth Edition. David M. Taylor, Thomas R. E. Barnes and Allan H. Young. © 2025 David M. Taylor. Published 2025 by John Wiley & Sons Ltd. Chapter 4 Introduction Mental and behavioural problems caused by psychoactive substance use are common. The World Health Organization (WHO) in the ICD-­111 identifies acute intoxication, harmful use, dependence syndrome, ­withdrawal state (with or without delirium), substance-­induced psychotic disorder, substance-­induced amnesic disorder, other mental and behavioural disorders and unspecified mental and behavioural disorders as substance-­ related disorders. A wide range of psychoactive ­substances may be problematic including alcohol, opioids, benzodiazepines, gamma-­hydroxybutyrate/gamma-­butyrolactone (GHB/GBL), stimulants, new psychoactive substances (NPS) (including cathinones, ­synthetic cannabinoids and phenylethylamines), khat, nitrates, hallucinogens, anabolic steroids, nitazenes and tobacco. Substance misuse is frequently seen in people with severe mental illness (so-­called dual diagnosis) and personality disorder. In many adult psychiatry settings, dual diagnosis is the norm rather than the exception. In many parts of the world substance misuse services may be provided separately from general psychiatric services. The model of care in most addiction services means that patients who are not motivated to engage will not be assertively treated and followed up. Dual diagnosis teams are not universally available, resulting in suboptimal treatment of substance misuse for many patients with mental illness.2 According to the ICD-­11, dependence syndrome is ‘a cluster of physiological, ­behavioural, and cognitive phenomena in which the use of a substance or a class of substances takes on a much higher priority for a given individual than other behaviours that once had greater value’. A definite diagnosis of dependence should only be made if at least three of the following have been present together in the last year: ■ ■compulsion to take substance ■ ■difficulties controlling substance-­taking behaviour ■ ■physiological withdrawal state Addictions and substance misuse