Substance related disorder involves recurrent use of drugs and other substances. The drugs tend to alter the way person feel, think or behave. Substance abuse involves extensive and continuous use of substance which results in hazardous behaviour. Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition (Text Revision) recognises that maladaptive pattern of substance use leads to distress and disrupts normal functioning of the person. There is recurrent use resulting in failure to fulfil duties.
The person engages in physically dangerous activities and may face legal consequences. A psychoactive substance is chemicals or drugs which act on the central nervous system and alter the functioning of the brain and effects perception, mood, consciousness and behavior. Psychoactive substance includes alcohol, ecstasy, tobacco, marijuana, cocaine, LSD and heroine etc.
In Pavlovian conditioning, neutral stimulus is paired with unconditioned stimulus which elicits unconditioned response. After repeated pairing, the neutral stimulus becomes conditioned stimulus and elicits the response which was originally produced by unconditioned stimulus. Conditioned stimulus produces response which is referred as conditioned response. In operant conditioning, learning occurs by reinforcement. Behaviours with desirable consequences are reinforced. Operant conditioning uses reward or punishment for reinforcing behaviour.
Substance use is learned behaviour. Pavlovian conditioning processes play an important role in the development, maintenance and relapse of alcohol and other substance dependence possibly by influencing thought and behaviour. As a result of pavlovian conditioning, a person might associate environmental stimulus with response to certain drug. Environmental stimulus becomes conditioned stimulus after repeated pairing with the drug and produces physiological changes which were initially produced by the drug. Environmental stimulus may act as relapse trigger and lead to addiciton. Environmental cues that have been associated with drug use can produce physiological changes that regular user might interpret as withdrawal symptoms or drug craving. Individuals with substance use disorder pay attention to substance related triggers. Environmental cues are associated with craving and may lead to relapse (Field, Marhe and Franken, 2014).