Drug Use, Addiction, Tolerance, Withdrawal and Relapse

Occasional or ‘recreational’ use of drugs of abuse may result in pleasurable effects such as euphoria and reduced anxiety. Regular use leads to dependence and addiction through a series of steps. Initial drug-seeking behaviour and positive reinforcement increase use and cause neural adaptations. Adaptations in key parts of the brain manifest as tolerance, where more drug is required to achieve the same effects, and to withdrawal in the absence of the drug. With repetitive use comes attribution of salience to the drug. Associated environmental items become conditioned stimuli that drive further, repetitive drug-seeking behaviour.