Addiction involves four factors: drug use becomes automatic habit, drug cues trigger intense cravings, natural rewards lose appeal, and negative emotions worsen. Repeated drug exposure rewires the brain's reward system, shifting control from flexible decision-making to rigid habit circuits while impairing the prefrontal cortex.
So according to a prominent hypothesis of addiction, there's 4 factors that play a major role. So you have the formation of habits, the increased effects of drug cues, stressors, and priming. Priming is, for example, a priming dose such as a small sip of wine that kind of makes you want to drink more. Then reduced choice of alternative non-addictive non-drug rewards, such as food or sex or other things that are usually fun, and increased negative affect, and possibly for some impaired cognitive control. So to put this into perspective concerning the course of addictive disorders, habit formation is when goal-directed and flexible recreational drug use is gradually replaced by rigid habits and automatized drug intake. I will quickly outline the neuromechanisms in addiction. So the increased effect of exposure to drug cues, stress, and priming doses on drug intake, which I talked about before, are associated with sensitization processes in brain regions that are involved in reward processing. In those, chronic drug intake is associated with increased dopamine release, which is a very important neurotransmitter that has to do with wanting and liking something, and a reorganization of ventral to dorsal striatal loop, which impair flexibility in behavior and promote this habitual drug intake. The possible impaired cognitive control is attributed to heritable as well as environmental vulnerability factors that interact with the neurotoxic and adaptive changes that come with the drug consumption. As you know, alcohol and other drugs of abuse can be very neurotoxic. And these changes are usually in the prefrontal cortex and related brain regions. In parallel, there's neuroadaptive processes within the limbic and the stress hormone systems that contribute to impulsive drug seeking and drug choice compared to alternative naturally found rewards.
