Could the link between drug addiction in adulthood and substance use in adolescence result from a blurring of the boundaries between incentive and hedonic processes?

Abstract

There is a broad consensus that the development of drug addiction in adulthood is closely linked to the onset of drug use in adolescence. However, the relationship between drug exposure during adolescence and subsequent vulnerability to addiction is yet to be fully understood. This review will first use evidence from adult studies on reward and addiction to give an up-to-date reference point of normal reward-circuitry and the maladaptive changes that later occur in addiction. This will then be compared with current evidence from adolescent studies on reward-circuitry. Similarities between the reward processes governing characteristic behavioral traits in adolescence and the reward profile in adult addiction could help to explain why the risk of later developing addiction is increased when substance use is initiated in adolescence. We argue that the age of onset is a major risk factor in the development of substance use disorder due to a blurring of the boundaries between incentive and hedonic processes, which occurs during adolescence. A deeper understanding of the processes that mediate this blurring could open new avenues for the prevention and treatment of adult drug addiction.

Keywords: addiction; compulsive; dopamine; impulsive; opiate.

Figure 1

The dissociation between incentive and hedonic processes. Incentive processes govern the appetitive “wanting” stage of motivated behavior. It is widely recognized that incentive processes are mediated by dopaminergic signaling. On the other hand, hedonic processes govern the consummatory phase of motivated behavior. They control liking for rewards and are thought to be mediated by opioid signaling.

Figure 2

The blurred dissociation between incentive and hedonic processes. The blurring between incentive and hedonic processes that is seen neurobiologically in adolescence is also seen behaviorally as there is a blurring of the boundaries between the behavioral trait’s sensation-seeking (SS) and impulsivity (I). It can be hypothesized that adolescents who score highly on this constellation of blurred traits may be at greater risk of developing addiction later in life.