As humans, we continuously seek out things that can produce pleasurable feelings. One of the few ways to attain this feeling of euphoria or pleasure is by consumption of chemical substances. However, continuous consumption of these substances can lead to development of dependence towards them and this is more commonly known as addiction. Currently, the cost of social and economic impacts due to drugs of abuse addiction sums up to more than $740 billion annually (National Institute on Drug Abuse, 2017). Despite this, the clear neurophysiological mechanisms underlying development and progression of addiction is still unknown.

Addiction can be defined as repeated self-administration of alcohol or other drugs (AOD’s) despite knowledge of adverse medical and social consequences and attempts to abstain from AOD use (Robert & Koob, 1997). Initial intake of drug may be due influenced by genetic, psychosocial or environmental factors however, subsequent doses is most probably caused by action on drug on the brain to induce the drug-seeking behaviour. Addiction is comprised of three stages which are ‘binge/intoxication’, ‘withdrawal/negative affect’, and ‘preoccupation/anticipation’ as seen in Figure 1 (Koob &Volkow, 2010).

Figure 1. The Three stages of addiction and brain areas each stage associates with (Herman & Roberto, 2015)

‘Binge/intoxication’ refers to the consistent intake of drug after initial dose which may cause decrease in dopamine release after each intake due to sensitization. This will then lead to ‘withdrawal/negative affect’ stage where absence of drug will cause a decrease in dopamine causing anxious and restless feelings resulting in the craving or ‘preoccupation/anticipation’ stage. Two major factors known to modulate these behavioural changes are reinforcement where a stimulus increases the chance of response and neuroadaptation, the process by which neuronal structures change in response to drug exposure. Modulation of these factors motivates initial response to a drug and formation of long-term craving however, relapse is thought to be caused by permanent neuroadaptations that will cause discomfort during withdrawal (Robert & Koob, 1997)