Drug dependence

Drug dependence may occur when a person continues to use drugs— legal or illegal—even though their drug use causes them significant problems. 

It is regarded by many as a medical condition or a disorder not directly under the control of the individual. The term 'addict', with its negative implications, is not used any longer. There have been recent changes to the terminology used to describe this pattern of use, with the terms alcohol/drug abuse and alcohol/drug dependence being replaced by a single term 'alcohol/drug use disorder'/ However, as drug dependence is a commonly understood term, for the purposes of this website, the term dependence will be used to describe this pattern of use

This pattern of alcohol or drug use may be diagnosed by the presence of two or more symptoms, including:

  • a strong desire to take the drug, spending a signifcant amount of time
    obtaining the drug, using it, and/or recovering from its effect
  • difficulties in controlling its use – unsuccessful attempts to cut down
    or stop, or using more of the drug or using it for longer than intended
  • persisting in its use despite harmful physical or psychological consequences
  • a higher priority given to drug use than to other activities
    and obligations – social, recreational and work
  • the development of a tolerance to the drug (see below)
  • experiencing symptoms of withdrawal when the drug use is stopped
    or reduced (see below).

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After using a drug for a while, a person may find that:

  • they need to take more of the drug to get an effect that they previously got with less, or
  • the drug simply becomes less effective in producing the desired effect.

This is called tolerance.


When a person who has been using a drug stops taking it, or reduces the dose, they may experience a physical and/or psychological reaction. This is called withdrawal. Because the person has become tolerant to the drug's effects, they have been taking the drug just to feel 'normal'.

When the drug is removed from their body, withdrawal can be very unpleasant, producing symptoms such as tremors, sweating and vomiting, as well as strong craving for the drug. For some drugs and some individuals, medical supervision during withdrawal is necessary.

The strength of the withdrawal vries, depending on:

  • the individual person
  • the drug they have been using
  • how frequently and for how long a person has been using the drug.

Withdrawal symptoms can make it very difficult for a user to stop or reduce their drug use and it is a common reason for people to relapse into drug use.


The process by which the body eliminates a drug and its immediate physical and psychological effects is called detoxification.

Detoxification usually leads to some level of withdrawal, and withdrawal management (sometimes involving medical assistance) may be required. Anti-anxiety drugs such as benzodiazepines are sometimes prescribed for a short time during medically-supervised withdrawal.