We thank Corinne Lim for her expert contribution to the literature and cross-checking of the citations to the literature.
Diagnosis and classification are ways in which we make sense of our clinical and epidemiological observations and help communicate our findings to others. These systems provide an important basis for the prevention of human disorders and for their management in people who develop them. This applies as much to substance use and other addictive disorders as to other conditions. Indeed, careful diagnosis and categorization are particularly important in the addictions, given the great variety of psychoactive substances (of different pharmacological and chemical classes), the wide spectrum of use and misuse of these substances, and the innumerable complications that arise from such use. Precision in diagnosis is clearly vital for clinical purposes, and epidemiological researchers and health statisticians need valid and cross-culturally applicable diagnoses.
This chapter explores three distinct but overlapping areas. In the first section, there is a review of the nature of psychoactive substance use, misuse, and dependence. The alternative, indeed competing, conceptualizations of these disorders over the past century are discussed. There follows an account of how the present diagnostic and classification systems have been developed. The next section describes the main substance use diagnoses in the Diagnostic and Statistical Manual of Mental Disorders (DSM), currently in its Fifth Edition (DSM-5), and the previous Fourth Edition (DSM-IV), and the International Classification of Diseases (ICD), including the Tenth Revision (ICD-10) and the Eleventh Revision (ICD-11). This section includes DSM-5 Substance Use Disorder and ICD-10/11 Substance Dependence and Harmful Substance Use, and also hazardous or risky use and the main substance-induced disorders. The final section is an account of practical ways of making these diagnoses that are applicable to clinical practice.
The Nature of Substance Use Disorders
Given the many professional disciplines that have contributed to our understanding of psychoactive substances and their effects, it is not surprising that scientists and practitioners have drawn upon different traditions to explain the nature of the disorders related to substance use. In addition, there have been many lay interpretations. In the 19th century, a popular conceptualization of excessive alcohol and drug use was that it represented a failure of morals or character. This notion, although superseded in the professional literature of the later 20th century, continues to influence community and political views as to the nature of substance use disorders and that of people with them.
In the First Edition of the DSM, published in 1952, substance misuse was included in the personality disorders. Drug addiction was not specifically defined, but there was a statement that “Addiction is usually symptomatic of a personality disorder. The proper personality classification is to be made as an additional diagnosis.” The Second Edition of the DSM, published in 1968, still had substance use disorders classified within the personality disorders. No specific definitions or criteria were provided, and there was little description of the conditions, although the text included a statement that “the best direct evidence for alcoholism is the appearance of withdrawal symptoms” and that the diagnosis of drug dependence required “evidence of habitual use or a clear sense of a need for the drug.”
The Disease Concept
A different tradition saw substance misuse as reflecting a disease process, which was biologically determined, resulting in the individual having some type of idiosyncratic reaction to alcohol or a drug, and having a relatively predictable natural history. This conceptualization influenced and was subsequently embraced by the self-help movements, such as Alcoholics Anonymous. Jellinek developed the concept of the disease of alcoholism in the 1940s and 1950s, although in his later work he increasingly recognized the role of environmental influences. Over many years in the latter half of the 20th century, the concept that substance misuse might represent a disease process was dismissed by many scientists and professionals. Likewise, the role of genetic predisposition was thought to be inconsequential, with the familial aggregation of substance misuse explained by cultural influences, role-modeling, or malfunction within families.
Epidemiological and Sociological Formulations
A third tradition may be described as the epidemiological and sociological one. Put simply, substance misuse and problems arise fundamentally because of the overall level of use of that particular substance in society. In the 1950s, Ledermann proposed a relationship between the level of alcohol consumption in the community and the prevalence of alcoholism. The level of use is, in turn, influenced by the availability of alcohol, its manufacture and distribution, its price (importantly), and cultural traditions and sanctions. Inherent in these conceptualizations is that individual pathology is considered of secondary importance. The social constructionist school views substance use problems as disaggregated, with no special relationship among them. This school of thought was concerned about the stigma attributable to diagnostic labels and the potential of treatment as a form of social control.
The 1970s saw the rise of social-cognitive theory as an influential paradigm to explain the development and resolution of alcohol and drug problems. This school of thought teaches that the (many) influences that determine behavior in general apply to the uptake of substance use and the development of disordered use. Positive consequences encourage repeated use, and negative ones the opposite. Patterns of substance use behavior can become established in this way, but, equally, repetitive substance use can be “unlearnt.” This led to the development of a range of cognitive behavioral therapies, some of which were aimed at moderated or “controlled” substance use.
The need for an understanding of substance misuse that spanned these various discipline-bound conceptualizations and terms was largely met by the formulation of the concept of a “substance dependence syndrome” originally proposed with regard to alcohol dependence by Edwards and Gross in 1976. The basis of the dependence syndrome was a clinical description of key clinical features in a way that was essentially atheoretical and was not based on any particular etiological understanding of the disorder, be it biological, behavioral, or sociological. Rather, certain experiences, behaviors, and symptoms related to repetitive alcohol use were identified as tending to cluster in time and to occur repeatedly. The advantage of a descriptive account of dependence is that it can accommodate etiological models but not be beholden to them.
The concept of the dependence syndrome has been very influential. It has been shown to apply to many other psychoactive substances that have the potential for reinforcement of use, including benzodiazepines, illicit and prescribed opioids, cannabis, inhalants, psychostimulants such as cocaine and the amphetamines, nicotine, caffeine, and anabolic steroids. a
a References 24, 42, 48, 50, 66, 70, 72.It also may apply to repetitive behaviors that do not involve self-administration of a psychoactive substance. These include excessive gambling, excessive online (computer/Internet) gaming, and possibly excessive shopping and exercise.
Until the development of the DSM-5, Substance Dependence was at the heart of the present classification systems of psychoactive substance use disorders. It takes center stage in ICD-10 and ICD-11, and it was the master substance use diagnosis in DSM-IV, having been introduced into the Diagnostic and Statistical Manual of Mental Disorders, 3rd Edition, Revised (DSM-IIIR). However, it was removed as such from DSM-5, being replaced by Substance Use Disorder as the central diagnosis. Eight of the 11 criteria are those of Substance Dependence.
Arguably the most important developments in our understanding of the nature of substance misuse in recent years have been in neurobiological processes and especially the neurocircuitry of dependence/addiction. This has been complemented by findings from genetic research that supports what some term the “brain disease model” of addiction.
There is now compelling evidence that repeated use of psychoactive substances leads to powerful and enduring changes in cortico-mesolimbic reward, stress, and control systems. In turn, these result in reinforcement and perpetuation of such use. Repeated exposure to the substance may invoke both long-term potentiation in which transmission of signals increases, and long-term depression, in which signal transmission decreases. Neuroplastic changes have been found in the nucleus accumbens (a crucial brain-reward region), in the dorsal striatum (implicated in encoding of habits and routines), the amygdala (involved in emotions, stress, and desires), and the hippocampus (involved in memory).
The key neurobiological changes that underpin dependence/addiction include:
Activation and then blunting of brain reward systems, particularly involving dopaminergic transmission and opioidergic transmission. This has the effect of resetting the reward systems such that larger amounts of the substance are needed to produce the desired effect. Natural rewards are not as reinforced because of the relatively low response from these systems. During withdrawal, activation of the brain regions involved in emotion results in negative mood and enhanced sensitivity to stress.
Recruitment of brain stress systems, including those subserved by glutamate neurotransmission and corticotropin-releasing factor (CRF) and suppression or uncoupling of antistress systems. Disruption of dopamine and glutamate systems and stress control systems are related to CRF and dynorphin.
Alterations occur in the salience of the substance involved, with its climbing up the “ladder of priorities” in the person’s life. This has the effect of relegating other interests, activities, and responsibilities to the periphery of the person’s life.
Impairment of inhibitory control pathways from the prefrontal cortex to the mesolimbic systems, resulting in impaired decision-making capacity, and an inability to balance the strong desire for the substance with the will to abstain. This triggers relapse.
Dopamine release leads to induction of neuronal plasticity, which underpins associative learning and memories that result in repetitive substance use even though the original personal triggers and environmental influences have changed. Dependence/addiction may be construed as an “internal driving force” that results from repeated exposure to a psychoactive substance and in turn leads to further repetitive substance use, which is now self-perpetuating and typically occurs even in the face of harmful consequences. Developments in neuroscience research into the mechanisms of addiction have been summarized in a monograph published by the World Health Organization (WHO) and by Volkow, Koob, and colleagues from the US National Institutes of Health.
Biological and Social Risk Factors
Investigations into possible genetic influences have accompanied this research on neural circuitry. Biometric genetic studies have shown that children born of parents with substance dependence are more likely to have substance dependence themselves and that this is largely explained by genetic transmission rather than environmental factors. Genomic analysis in human and laboratory animals has identified several areas of the genome where mutations are associated with increased risk of substance use disorders.
Patients with certain mental illness such as mood disorders, trauma-related disorders, attention-deficit/hyperactivity disorder, psychotic disorders, and anxiety states are at higher risk of substance use disorders. A key finding in recent years has been the central role of abuse and trauma in childhood and adolescence. Social and environmental influences on substance use disorders include: poor familial and social supports, early exposure to substance use, risk taking, novelty seeking, peer pressure, socially stressful environments, easy availability of substance, and permissive attitudes to substance use.
Achieving a Synthesis
It is clear that psychoactive substance use exists as a continuum in society, but it is equally clear that within this spectrum it is possible—and important—to define disorders that have a distinct set of physiological and behavioral features. Substance dependence is a syndrome that occurs in response to repeated and typically high-level alcohol or other substance use, is driven by a profound resetting of key neurobiological systems, is compounded by impaired executive control, and leads to continuing and damaging substance use. As indicated, it is a central diagnosis in the ICD system and is at the core of DSM-5 Substance Use Disorder.
Other forms of repetitive substance use seem not to have these neurobiological changes—at least not to the extent of dependence. They appear to be influenced primarily by factors that affect many types of repetitive human behavior. These include expectations of a substance’s effect, responding to learned associations with substance use, and many and varied environmental influences, including peer group pressure, ethnic and workplace culture, and the influences of availability and accessibility of alcohol and various drugs.
Separate from the dependence syndrome and nondependent forms of substance misuse are the multiple consequences of substance misuse. These may be physical, neurocognitive, mental, and social. They typically reflect the adverse effects of the substance, the mode and means of administration of the substance, and/or the implications of the dependence processes. They include disorders of the heart, lungs, gastrointestinal tract, liver, muscles, brain, and peripheral nerves. Mental health complications include mood and anxiety disorders and various psychoses. Social complications encompass interpersonal, financial, occupational, and legal difficulties.
Substance Use Diagnoses in the DSM and ICD Systems
Although many different systems of diagnosis and classification have been proposed for substance use disorders over the years, two have international recognition and a third is in widespread use among specialist addiction services. The two internationally recognized systems are the Diagnostic and Statistical Manual of Mental Disorders , of which the current version is DSM-5, 4 and the International Classification of Diseases published by WHO, the current versions being the Tenth Revision (ICD-10), and with the Eleventh Revision (ICD-11) having been published in 2019 and scheduled for implementation in 2022. The International Classification of Diseases is a classification of all diseases, injuries, and causes of death. The DSM system specifically covers mental, substance use, and behavioral disorders. The third diagnostic system is that published by the American Society of Addiction Medicine (ASAM), which has been endorsed in its essentials by the International Society of Addiction Medicine (ISAM).
Comparisons of DSM-IV, DSM-5, ICD-10, and ICD-11
There are substantial differences in the diagnostic entities that feature in DSM-5 compared with DSM-IV and also ICD-10, and there are comparable differences between DSM-5 and ICD-11.
The DSM and ICD systems have as primary subclassifications (1) the substance or group of substances implicated ( Table 5.1 ) and ( Table 5.2 ), the nature (type) of the disorder that is present (see, for example, Fig. 5.1 , which depicts the structure of ICD-11). In DSM-5 are included 10 separate classes of substance, namely alcohol, caffeine, cannabis, hallucinogens, inhalants, opioids, sedatives and anxiolytics, stimulants, tobacco, and other substances. The DSM-IV diagnosis of “Polysubstance Dependence” has been eliminated (see Table 5.1 ). ICD-10 is similar in its coverage, but it subdivides psychostimulants into cocaine on the one hand, and other stimulants such as amphetamine-type compounds and caffeine on the other. Multiple drug use is combined with other psychoactive substances. ICD-11 has expanded the range and number of substance categories, reflecting its role as an international system for monitoring trends in substance use as well as a clinical manual (see Table 5.1 ). There are three separate psychostimulant categories, covering cocaine, amphetamines, and caffeine respectively, a separate category for empathogens such as methylenedioxy-methamphetamine (MDMA or “Ecstasy”) and for dissociative drugs such as phencyclidine and ketamine. A recent development has been to include new psychoactive substances, namely synthetic cannabinoids and synthetic cathinones in separate groups.
|Sedatives, hypnotics, or anxiolytics
|Sedatives, hypnotics, or anxiolytics
|Sedatives, hypnotics, or anxiolytics
|Other stimulants including caffeine
|Stimulants including amphetamines, methamphetamine, or methcathinone
|The stimulants category in DSM-5 includes amphetamine-type substances, cocaine, and other or unspecified stimulants. For some diagnoses the type of substance can be specified.
|Hallucinogens, Empathogens, and Dissociative Drugs
|Dissociative drugs including ketamine and phencyclidine
|In DSM-5 there are separate descriptions for phencyclidine and for other hallucinogens. MDMA is classified under other hallucinogens.
|MDMA and related drugs including MDA
|Multiple drug use and use of other psychoactive substances
|The category Polysubstance Use does not appear in DSM-5 or ICD-11
|Other and Unknown Substances
|Other or unknown substances
|Other specified psychoactive substances
|Unknown or unspecified psychoactive substances
|There is no category for unknown or unspecified substances in DSM-IV
|DSM-5 Substance Use Disorder
|ICD-10 Substance Dependence
|ICD-11 Substance Dependence
|A maladaptive pattern of substance use, leading to clinically significant impairment or distress, as manifested by three or more of the following occurring at any time in the same 12-month period.
|A problematic pattern of substance use leading to clinically significant impairment or distress, as manifested by at least two of the following occurring within a 12-month period
|A cluster of physiological, behavioral, and cognitive phenomena in which the use of the substance takes on a much higher priority for a given individual than other behaviors that once had greater value. Three or more of the following [six] manifestations should have occurred together for at least 1 month, or occurred together repeatedly within a 12-month period.
|A disorder of regulation of the substance use arising from repeated or continuous use of the substance. The characteristic feature is a strong internal drive to use the substance. The diagnosis requires two or more of the three central features to be present in the individual at the same time and to occur repeatedly over a period of at least 12 months or continuously over a period of at least 1 month.
|No equivalent criterion mentioned in text
|Craving or a strong desire or urge to use the substance
|A strong desire or sense of compulsion to take the psychoactive substance (craving or compulsion)
|1. Impaired control over substance use—in terms of the onset, level, circumstances, or termination of use, and often, but not necessarily, accompanied by a subjective sensation of urge or craving to use the substance.
|There is persistent desire or unsuccessful attempts to cut down or control substance use
|There is persistent desire or unsuccessful efforts to cut down or control substance use
|No equivalent criterion but text states that the subjective awareness of compulsion is most commonly seen during attempts to stop or control substance use.
|The substance is often taken in larger amounts or over a longer period than was intended
|The substance is often taken in larger amounts or over a longer period than was intended
|Difficulties in controlling substance-taking behavior in terms of its onset, termination, or levels of use (loss of control)
|Important social, occupational, or recreational activities are given up or reduced because of drinking or psychoactive substance use.
|Recurrent substance use resulting in a failure to fulfill major role obligations at work, school, or home
|Progressive neglect of alternative pleasures and responsibilities because of psychoactive substance use, or increased amount of time necessary to obtain or take the substance or to recover from its effects.
|2. Substance use becomes an increasing priority in life such that its use takes precedence over other interests or enjoyments, daily activities, responsibilities, or health or personal care. It takes an increasingly central role in the person’s life and relegates other areas of life to the periphery. Substance use often continues despite the occurrence of problems.
|A great deal of time is spent in activities necessary to obtain the substance, use the substance or recover from its effects.
|A great deal of time is spent in activities necessary to obtain the substance, use the substance or recover from its effects
|Subsumed in the above criterion.
|The substance use is continued despite knowledge of having a persistent or recurrent physical or psychological problem that is likely to have been caused or exacerbated by the substance
|Substance use is continued despite knowledge of having a persistent or recurrent physical or psychological problem that is likely to have been caused or exacerbated by that substance
|Persisting with substance use despite clear evidence of overtly harmful consequences.
|Tolerance: as defined by either (a) a need for markedly increased amounts of the substance to achieve the desired effects or (b) markedly diminished effect with continued use of the same amount of the substance.
|Tolerance is defined by either of the following: (a) a need for markedly increased amounts of the substance to achieve intoxication or desired effect (b) a markedly diminished effect with continued use of the same amount of the substance
|Tolerance: such that increased doses of the psychoactive substances are required to achieve effects originally produced by lower doses.
|3. Physiological features (indicative of neuroadaptation to the substance) as manifested by (i) tolerance, (ii) withdrawal symptoms following cessation or reduction in use of that substance, or (iii) repeated use of the substance (or pharmacologically similar substance) to prevent or alleviate withdrawal symptoms. Withdrawal symptoms must be characteristic for the withdrawal syndrome for that substance and must not simply reflect a hangover effect.
|Withdrawal as manifested by either (a) the characteristic withdrawal syndrome for the substance or (b) the same (or a closely related) substance is taken to relieve or avoid withdrawal symptoms.
|Withdrawal is manifested by either (a) the characteristic withdrawal syndrome for the substance or (b) the substance (or a closely related substance) is taken to relieve or avoid withdrawal symptoms
|A physiological withdrawal state when substance use has ceased or been reduced, as evidenced by the characteristic withdrawal syndrome for the substance; or use of the same (or a closely related substance) with the intention of relieving or avoiding withdrawal symptoms.
Former DSM-IV abuse
|Continued substance use despite having persistent or recurrent social or interpersonal problems caused or exacerbated by the effects of the substance (e.g., arguments with spouse about consequences of intoxication, physical fights)
|Continued substance use despite having persistent or recurrent social or interpersonal problems caused or exacerbated by the effects of the substance.
|To some extent subsumed in criterion no. 4.
|To some extent subsumed in criterion no. 2.
Former DSM-IV abuse
|Recurrent substance use in situations in which it is typically hazardous (e.g., drink driving)
|Recurrent use in situations in which it is physically hazardous
|No equivalent criterion
|No equivalent criterion
Former DSM-IV abuse
|Recurrent substance use which results in failure to fulfil major obligations at work, school or home
|Important social, occupational or recreational activities are given up or reduced because of substance use
|To some extent subsumed in criterion no. 4.
|To some extent subsumed in criterion no. 2.
|Former DSM-IV abuse, now omitted
|Recurrent substance-related legal problems (e.g., driving an automobile or operating a machine when impaired by substance use)
The range of disorders due to substance use can be subdivided conceptually into those that represent (1) the actual use of the substance, whether one-off or repeated, and its immediate effects, and (2) those which reflect its complications, including disease processes in the brain and the rest of the body (see Fig. 5.1 ). Among the former are the DSM-5 Substance Use Disorder, DSM-IV Substance Dependence, and ICD-10 and ICD-11 Substance Dependence. Substance dependence has at its core a psychobiological driving force to consume the substance. In DSM-5, a decision was made to combine (essentially) DSM-IV Substance Abuse and Substance Dependence into a broader diagnostic entity known as “Substance Use Disorder” (see Table 5.2 ).
As described above, the entity of substance dependence arose largely from the work of Griffith Edwards at the Maudsley Hospital in London from the mid-1970s onward. It emphasizes a central syndromal grouping of features such as craving, impaired control over substance use, stereotyping of use, and prioritizing of substance use, together with physiological features of tolerance and withdrawal. This central syndrome replaced the much broader notions of alcoholism and addiction, which had typically incorporated some of the mental and social complications as well as externalizing behaviors and denial of the problem. The existence of substance dependence has been supported by numerous studies of its psychometric properties. Applied first to alcohol it became accepted as applying to prescribed medications such as benzodiazepines and opioids and to a range of recreational and illicit drugs such as cannabis, heroin, and psychostimulants.
We now summarize the features and diagnostic criteria of the principal disorders due to substance use as appear in the four systems.
Substance Use Disorder (DSM-5)
In DSM-5, Substance Use Disorder is now the central diagnosis and represents essentially a combination of the diagnostic features of DSM-IV Substance Dependence and Substance Abuse (see Table 5.2 ), with one Substance Abuse criterion omitted and the ICD-10 criterion of craving added. This offers a simplified diagnostic system. In DSM-5, Substance Use Disorder is defined as a problematic pattern of substance use leading to clinically significant impairment or distress, manifested by at least two of the following 11 criteria occurring within a 12-month period:
The substance is often taken in larger amounts over a longer period than was intended
There is persistent desire or unsuccessful efforts to cut down or control substance use
A great deal of time is spent in activities necessary to obtain the substance, use the substance, or recover from its effects
Craving or a strong desire or urge to use the substance
Recurrent substance use resulting in a failure to fulfil major role obligations at work, school, or home
Continued substance use despite having persistent or recurrent social or interpersonal problems caused or exacerbated by the effects of the substance
Important social, occupational, or recreational activities are given up or reduced because of substance use
Recurrent substance use in situations in which it is physically hazardous
Continued substance use despite knowledge of having a persistent or recurrent physical or psychological problem that is likely to have been caused or exacerbated by that substance
Tolerance as defined by either of the following: (a) a need to markedly increase amounts of substance to achieve intoxication or desired effect, or (b) a markedly diminished effect with continued use of the same amount of substance
Withdrawal as manifested by either of the following: (a) the characteristic withdrawal syndrome for the substance or (b) the substance (or a closely related substance) is taken to relieve or avoid withdrawal symptoms.
The severity is graded on the number of criteria met viz mild: 2–3; moderate 4–5; severe: 6 or more (see Table 5.2 ).
This aggregation is supported by analyses of the components of the DSM-IV diagnoses of Substance Dependence and Substance Abuse, using item response theory (IRT) and similar analyses. It also avoids what were termed “diagnostic orphans,” persons who fulfilled only two of the DSM-IV Substance Dependence criteria. The problem is that Substance Use Disorder is a very broad and heterogeneous condition for diagnosis. Indeed one can calculate that there are more than 2000 combinations of the diagnostic criteria that fulfill the requirements for Substance Use Disorder, which detracts from the concept that it is syndromal in nature. There is a risk of it being so broad and heterogeneous that it is a less useful entity than substance dependence was in terms of determining treatment. This change has occurred despite DSM-IV Substance Dependence being a psychometrically robust syndrome, as identified in the research phase of the DSM-5 developmental process. Two examples of these are the fact that dependence is required on heroin or other opiates for there to be justification in prescribing replacement opioid agonist therapy with methadone or buprenorphine. In a similar vein, alcohol pharmacotherapies such as naltrexone and acamprosate have been trialled among people with alcohol dependence rather than the broader entity that is alcohol use disorder.
Substance Dependence (ICD-10, ICD-11, and DSM-IV)
Substance dependence is the central disorder of repetitive substance use in ICD-10 and remains so in ICD-11. It emphasizes a central syndromal grouping of features such as impaired control over substance use, craving, prioritizing of substance use, together with physiological features of tolerance and withdrawal. These features are found in DSM-5 Substance Use Disorder, but what is less emphasized in the latter’s diagnostic criteria is the clustering and repeated experience of these central experiences. As described earlier, this central syndrome replaced broader notions of alcoholism and addiction that had typically incorporated some of the mental and social complications as well as externalizing behaviors and denial of the problem.
The definitions and diagnostic guidelines in ICD-10 and ICD-11 are shown in Table 5.2 . Substance Dependence in ICD-11 is described as:
A disorder of regulation of substance use arising from repeated or continuous use of that substance. The characteristic feature is a strong internal drive to use the substance, which is manifested by impaired ability to control use, increasing priority given to use over other activities and persistence of use despite harm or negative consequences. These experiences are often accompanied by a subjective sensation of urge or craving to use the substance. Physiological features of dependence may also be present, including tolerance to the effects of the substance, withdrawal symptoms following cessation or reduction in use of the substance, or repeated use of the substance or pharmacologically similar substances to prevent or alleviate withdrawal symptoms. The features of dependence are usually evident over a period of at least 12 months but the diagnosis may be made if substance use is continuous (daily or almost daily) for at least one month.
Substance dependence in ICD-11 (see Table 5.1 ) requires the presence of two or more of the three diagnostic guidelines :
Impaired control over substance use —in terms of the onset, level, circumstances, or termination of use, often but not necessarily accompanied by a subjective sensation of urge or craving to use the substance.
Substance use becomes an increasing priority in life such that its use takes precedence over other interests or enjoyments, daily activities, responsibilities, or health or personal care. Substance use takes an increasingly central role in the person’s life and relegates other areas of life to the periphery. Substance use often continues despite the occurrence of problems.
Physiological features (indicative of neuroadaptation to the substance) as manifested by (i) tolerance, (ii) withdrawal symptoms following cessation or reduction in use of that substance, or (iii) repeated use of the substance (or pharmacologically similar substance) to prevent or alleviate withdrawal symptoms. Withdrawal symptoms must be characteristic for the withdrawal syndrome for that substance and must not simply reflect a hangover effect.
There are several reasons for retaining Substance dependence as a diagnostic entity, notably its excellent psychometric performance of ICD 10 Substance Dependence for all substance groups (reviewed in Saunders and Saunders and Janca ). In addition, it gives guidance to clinicians as to when pharmacotherapies are appropriate, including agonist maintenance for opioid use disorders. The research evidence for anti-craving, relapse-prevention and agonist maintenance treatments is based on controlled trials of these treatments in patients diagnosed with substance dependence (or in some cases the equivalent diagnosis of alcoholism or drug addiction).
The simplified ICD-11 guidelines have been found to be in almost perfect agreement with the ICD-10 and DSM-IV classifications of dependence, but not so much with DSM-5 Substance Use Disorder. Early indications are that DSM-5 captures different individuals in other systems. Initial data found that the moderate and severe subgroups of DSM-5 Substance Use Disorder (4–5 symptoms, and 6+ symptoms respectively) corresponded to DSM-IV and ICD-11 dependence, but there are emerging data that 5+ symptoms in DSM-5 might be the nearest equivalent to ICD-10 Substance Dependence.
The dependence syndrome applies to most psychoactive substances that have the potential for reinforcement of use (such as benzodiazepines, opioids, cannabis, psychostimulants, nicotine, caffeine, and anabolic steroids, as described earlier). However, elements of the syndrome are not necessarily applicable to all substances.
Typically substance dependence occurs in people who use large amounts of psychoactive substances repeatedly—for example, consuming alcohol in excess of 120 g/day (men) or 80 g/day (women). However, the diagnosis of substance dependence is not made primarily on the level of consumption.
Addiction as a Disease (ASAM, ISAM)
The American Society of Addiction Medicine (or ASAM) introduced its own definition of substance use disorders, aimed primarily at its clinician members. Reflecting its origins in regarding addiction as primarily a brain disease, its definition describes a severe, progressive disorder. Addiction is characterized as a primary, chronic disease of the brain reward, motivation, memory, and related circuits, with dysfunction in these circuits leading to characteristic biological, psychological, social, and spiritual manifestations. This is reflected in an individual pathologically pursuing reward and/or relief by substance use and other behaviors.
It is further defined by an inability to consistently abstain, impairment of behavioral control, craving, diminished recognition of significant problems with one’s behaviors and interpersonal relationships, and a dysfunctional emotional response. Like other chronic diseases, addiction involves cycles of relapse and remission. Without treatment or engagement in recovery activities, addiction is progressive and can result in disability or premature death. Other organizations have adopted this definition, including the International Society of Addiction Medicine (ISAM).
Harmful Substance Use (ICD-10 and ICD-11)
Repetitive substance use causing harm that does not fulfill the criteria for the dependence syndrome is referred to as “Harmful Substance Use” in ICD-10 and “Harmful Pattern of Use of a Substance” in ICD-11. It does not encompass substance use causing social problems, as the ICD system eschews the notion of a disorder that is defined by social criteria. Harmful substance use is a pattern of substance use that has caused damage to a person’s physical or mental health or has resulted in behavior leading to harm to the health of others. The pattern of substance use is evident over a period of at least 12 months if substance use is episodic or at least 1 month if use is continuous (i.e., daily or almost daily). Harm to the health of the individual occurs due to one or more of the following: (1) behavior related to intoxication; (2) direct or secondary toxic effects on body organs and systems; or (3) a harmful route of administration. It does not fulfill the criteria for the dependence syndrome.
The harmful effects may be acute or chronic. Examples of acute complications include fractures and other forms of trauma, acute gastritis, and acute psychotic symptoms following substance use. Chronic medical complications encompass liver disease (e.g., alcoholic liver disease or hepatitis C–induced liver disease following injecting drug use), cardiovascular diseases, respiratory diseases, various neurological sequelae, and many others. Examples of mental complications are depressive episodes secondary to heavy alcohol intake, and substance-induced psychosis. In what was a clear distinction from DSM-IV Substance Abuse, social consequences are insufficient by themselves to justify a diagnosis of Harmful Substance Use. Where a diagnosis of Substance Dependence has been made, the diagnosis of Harmful Substance Use cannot be made for the same substance over the same time period.
In the ICD 11, the concept of Harmful Substance Use is expanded by including behavioral problems that cause harm to others. These include any form of physical harm, including trauma, or mental disorder that is directly attributable to behavior related to substance intoxication.
A new diagnosis in ICD-11 is Episode of Harmful Substance Use. This would apply in situations where harm has been caused by use of a substance but there is no information about whether the person’s consumption represents a pattern of repeated use or a one-off episode.
Hazardous Substance Use and Related Conditions
The above diagnoses do not encompass the whole spectrum of repetitive, damaging (or potentially so) substance use and, therefore, pose limitations, especially for epidemiological purposes. In the work of a World Health Organization Expert Committee in the 1970s, several other conditions characterized by repetitive substance use were proposed to complement the dependence syndrome. However, only one, harmful substance use, survived to appear in ICD-10. Perhaps because of the breadth of the task, there have been few attempts to develop a classification system that encompasses the broad spectrum of substance use and misuse. The other condition that was introduced into WHO terminology and survived as a descriptive term but was not included in ICD-10 is “Hazardous Substance Use.” This is now included in ICD-11 as a factor affecting health status, in a chapter separate from the Disorders due to Substance Use.
As an example, Hazardous Alcohol Use, otherwise known as “unhealthy,” “at-risk,” “risky,” or “high-risk” use, is defined as use that increases the risk for health consequences, and has been operationalized in several countries. For example, in the United States, hazardous or at-risk use is defined in men as consumption of five or more standard 13 gram drinks in a day (e.g., 1.5 oz of 80 proof liquor, 4–5 oz of wine of regular strength, 12 oz of regular strength beer) or more than 14 drinks per week on average. Thresholds for women and for men 65 years or older, are four or more drinks in a day or more than seven in a week on average. A heavy drinking episode occurs whenever a person’s alcohol consumption meets or exceeds the daily threshold of five drinks or more for men and four drinks or more for women and for men 65 years and older. Heavy episodic drinking is defined as repeated heavy drinking episodes. Repeatedly consuming five or more (men) or four or more (women) US standard drinks (65 g and 50 g of alcohol, respectively) confers a risk of alcohol use disorders, acute and chronic illnesses, and injuries. In Australia, hazardous or risky consumption is defined presently as repeated daily consumption of more than two Australian standard drinks (20 g of alcohol) for both men and women. In other countries, it is variably defined . Some authorities state that a person should have at least two alcohol-free days per week as well as keeping below a specified level. In some Asian countries, hazardous or risky drinking indicates consumption at levels that lead to intoxication twice a month or more.
The application of hazardous or risky use to other substances has been slower. For nicotine (tobacco), it can be argued that there is no nonhazardous level of use. Likewise, because of uncertainties as to whether there is truly a safe or low-risk level of use for other substances, the concept has not been applied widely to illicit drugs such as cannabis, the amphetamines, cocaine, or heroin, although research on quantifying and establishing the risk of low-level cannabis use is emerging.
Hazardous substance use appeared in early drafts of ICD-10 but was omitted from the published version following the results of field trials that revealed an interrater reliability (kappa) coefficient of only 0.4. Because of the difficulty in operationalizing it, the diagnosis was considered to be open to misuse. The decision to omit hazardous substance use was also influenced by whether it represented a disease process, which was considered by many to be a prerequisite for inclusion in a classification system of diseases. For epidemiological and public health purposes, having a term that defines various levels or patterns of substance use as conferring risk is advantageous. Indeed, data from the National Epidemiologic Survey of Alcohol and Related Conditions indicate that hazardous alcohol consumption (defined as the United States 5+/4+ standard drink criterion) exists within the continuum of abuse and dependence criteria. As the frequency of this level of consumption increases, this experience moves along the severity continuum to overlap with dependence criteria.
In ICD-11, Hazardous Substance Use has been restored as a diagnostic entity. It is classified in a separate chapter as a “Factor influencing health status” and not included with the substance use disorders, which are in the chapter covering mental and behavioral disorders. In ICD-11 it is defined as:
A pattern of psychoactive substance use that appreciably increases the risk of harmful physical or mental health consequences to the user or to others to an extent that warrants attention and advice from health professionals. The increased risk may be from the frequency of substance use, from the amount used on a given occasion, from risky behaviors associated with substance use or the context of use, from a harmful route of administration, or from a combination of these. The risk may be related to short-term effects of the substance or to longer-term cumulative effects on physical or mental health or functioning. Hazardous substance use has not yet reached the level of having caused harm to the physical or mental health of the user or others around the user. The pattern of substance use often persists despite awareness of increased risk of harm to the user or to others.
In support of including hazardous use in a diagnostic system is the evidence that it can be defined and it responds to therapy, the evidence base for the effectiveness of interventions for hazardous alcohol consumption being particularly strong. Thus in a comprehensive diagnostic system, there are grounds for having a dependence category, a nondependence disorder that is of clinical consequence, and a subthreshold disorder that indicates risk to individuals and populations.
The term “unhealthy alcohol use” has been introduced as an umbrella term that encompasses the whole range of disorders of alcohol use, including those at the severe end such as dependence through to alcohol use that poses a risk for the individual but where no harm has occurred. This is a valuable concept and a practical means of grouping all the above diagnoses.
Substance Intoxication (DSM-IV, DSM-5, ICD-10, and ICD-11)
Substance Intoxication ( Table 5.3 ) is defined in DSM-5 as a reversible substance-specific syndrome due to (a) recent ingestion of a substance, (b) clinically significant problematic behavioral or psychological changes that develop during, or shortly after use, and (c) the signs and symptoms are not attributable to another medical condition and are not better explained by another mental disorder, including intoxication with another substance. ICD-11 defines substance intoxication as:
a clinically significant transient condition that develops during or shortly after the consumption of a substance that is characterized by disturbances in consciousness, cognition, perception, affect, behavior, or coordination. These disturbances are caused by the known pharmacological effects of the substance and their intensity is closely related to the amount of the substance consumed. They are time-limited and abate as the substance is cleared from the body.