Diagnosis and Classification of Substance Use Disorders

Personality Disorder

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.

Learned Behavior

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.

Clinical Syndrome

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.

Neurobiological Disorder

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:

• 1.

  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.

• 2.

  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.

• 3.

  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.

• 4.

  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.

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.

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.

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:

• 1.

  The substance is often taken in larger amounts over a longer period than was intended

• 2.

  There is persistent desire or unsuccessful efforts to cut down or control substance use

• 3.

  A great deal of time is spent in activities necessary to obtain the substance, use the substance, or recover from its effects

• 4.

  Craving or a strong desire or urge to use the substance

• 5.

  Recurrent substance use resulting in a failure to fulfil major role obligations at work, school, or home

• 6.

  Continued substance use despite having persistent or recurrent social or interpersonal problems caused or exacerbated by the effects of the substance

• 7.

  Important social, occupational, or recreational activities are given up or reduced because of substance use

• 8.

  Recurrent substance use in situations in which it is physically hazardous

• 9.

  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

• 10.

  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

• 11.

  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.