Substance misuse and dependence

Individual patterns of substance use range from occasional use, through to frequent and problematic use, to dependent use.

Many people who try illicit drugs do not become frequent users and many who become frequent users do not become dependent.

Multiple factors including availability of drugs, family and peer influences, and the environmental context contribute to decisions to initially try drugs. Once use has occurred, further factors contribute to the likelihood of developing dependence, including:

  • environmental factors (cues, conditioning, external stressors)
  • drug-induced factors (molecular neurobiological changes resulting in altered behaviours)
  • genetic factors through traits such as response to drug use, personality, concurrent psychiatric disorders.


Approximately one in four (23%) people who use heroin will become dependent. This is the second highest rate of dependence development after nicotine (32%) and is substantially higher than the equivalent rates for alcohol (15%), cocaine (15%) and cannabis (9%).

The way in which dependence develops is much the same for all drugs. Using daily or almost every day over a period of time leads to physical and psychological changes.

Physically, the body adapts or ‘gets used to’ having a drug on a regular basis. Eventually the drug is needed to function ‘normally’, and more is needed to get the same effect. When this happens, stopping or cutting down is very difficult because a person will start ‘hanging out’ or withdrawing. The drug may then be taken to ease or stop withdrawal occurring.

Psychologically, a person’s thoughts and emotions come to revolve around the drug. A person will ‘crave’ the drug (have strong urges to use), and feel compelled to use even though they know (or believe) it is causing them difficulties - perhaps financial or legal worries, relationship problems, work difficulties, physical health problems and psychological problems such as depression and anxiety.

The key elements of dependence are the loss of control over use, and continued use despite awareness of problems caused or exacerbated by the using behaviour. It is these aspects that make dependence particularly damaging to both the individual and the community. Treatment services prioritise people who are dependent because they are at high risk of harm to themselves and the community.

Diagnostic guidelines for drug dependence

ICD-10 criteria for a diagnosis of dependence require the presence of three or more of the following at some time during the previous year

Have any of the following been present in the previous 12 months?

Yes = 1,  No = 0

  1. A strong desire or sense of compulsion to take the substance (craving).
  2. Difficulties in controlling substance-taking behaviour (for example levels of use, starting or stopping).
  3. 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.
  4. Evidence of tolerance, such that increased doses of the psychoactive substance are needed in order to achieve the same effects as originally produced by lower doses.
  5. Progressive neglect of alternative pleasures or interests because of psychoactive substance use, increased amount of time necessary to obtain or take the substance or to recover from its effects.
  6. Persisting with substance use despite clear evidence of overtly harmful consequences.

Diagnostic and Statistical Manual of Mental Disorders (DSM)

The current Diagnostic and Statistical Manual of Mental Disorders (DSM) manual (DSM-5) is a scale with 11 items. The presence of at least two of these items in the past year indicates a substance use disorder. The severity of the disorder is then indicated by the number of items that are present: two or three criteria indicates a mild disorder, four or five criteria indicates moderate severity, and meeting six or more criteria indicates a severe disorder.

The definition of substance use disorder as a scale of increasing severity marks a substantial change in the DSM the previous version (DSM-IV) included separate definitions of substance abuse and substance dependence. Craving or a strong desire or urge to use a substance, has also been added as an item in the DSM-5.

Early remission is defined as at least three but less than 12 months without meeting the criteria (except craving), and sustained remission is defined as at least 12 months without meeting the criteria (except craving).

Harmful use

Harmful use is somewhat less severe than dependence. ICD-10 characterises harmful use as:

“A pattern of psychoactive substance use that is causing damage to health. The damage may be physical (as in cases of hepatitis from the self-administration of injected drugs) or mental (e.g. episodes of depressive disorder secondary to heavy consumption of alcohol)”.

Harmful use commonly, but not always, has adverse social consequences. Social consequences in themselves, however, are not sufficient to justify a diagnosis of harmful use. The diagnosis of harmful use can be made when amphetamine-type stimulant use does not meet the criteria for dependence.

Harmful use is defined in ICD-10 by the following:

  • There is clear evidence the substance use was responsible for (or substantially contributed to) physical or psychological harm, including impaired judgment or dysfunctional behaviour, which may lead to disability or have adverse consequences for interpersonal relationships.
  • The nature of the harm is clearly identifiable (and specified).
  • The pattern of use has persisted for at least one month and has occurred repeatedly within a 12-month period.
  • The disorder does not meet the criteria for any other mental or behavioural disorder related to the same drug in the same time period (except for acute intoxication).

The harms from substance misuse

The harmful effects of drug use relate both to the direct acute effects (intoxication and toxicity) as well as the health and social consequences of longer-term, chronic use.

The costs of drug use are broad, encompassing:

  • the loss of life through overdose, drug-related illness and injuries incurred while intoxicated
  • treatment of intoxication, injuries, overdose and other medical consequences of drug use
  • the transmission of disease, particularly HIV and hepatitis, mainly through use by injection
  • community loss due to criminal activity, particularly theft
  • law enforcement and judicial costs
  • loss of quality of life for users and their families, encompassing reduced socioeconomic status through loss of earning capacity, risk to children through neglect related to drug use, and negative impact on health and well-being of families
  • loss of social amenity in areas where drug use is prevalent.

My patient needs help

If you think your patient may have substance misuse problems, the first step is screening and assessment. Screening provides an indication of the level of risk associated with the patient’s pattern of substance use, and the type and intensity of intervention that would be appropriate.

For more information, go to:

Further information and advice

DACAS is available daily until 10pm. Out of these hours, medically urgent calls from a hospital based Medical Consultant or country hospital medical officer/GP will always receive a response.

This service does not provide proxy medical cover and cannot assume responsibility for direct patient care.