Addiction is characterized by a damaged “reward system” which prioritizes substance abuse to a degree that is self-damaging and difficult to scale back. In our previous post on AddictionNews, we learned that brain scans of children can fairly accurately predict later-life problems with gaming addiction. It is very likely scans can predict other addictive behavior as well, including substance abuse and thrill-seeking.

In the Adolescent Brain Cognitive Development (ABCD) Study, a diminished response in the brain’s caudate nucleus was correlated with “a blunted reward response and reduced sensitivity to everyday rewards.” It was also correlated with addictive gaming behavior developing years later. Researchers speculate the attraction to gaming is the flip side or the result of the diminished reward response.

Of course, it’s never that clear. A trio of researchers with the National Institute on Drug Abuse (NIDA) and the National Institute on Alcohol Abuse and Alcoholism (NIAAA) conducted a review of brain imaging studies looking at reward response and its relationship to addictive behaviors. They found two conflicting theories:

1. Increased sensitivity to reward drives compulsive behavior.

2. Decreased sensitivity to reward drives compulsive behavior.

Not all addictions and compulsions are alike. The association between blunted reward and the attraction to gaming found in the ABCD Study is also the dominant result of the NIDA review: “Positron emission tomographic (PET) studies of dopamine receptor density and dopamine release strongly support the reward-deficiency hypothesis,” the researchers conclude.

On the other hand, functional magnetic resonance imaging (fMRI) studies, both support and contradict the reward-deficiency hypothesis, and support and contradict the hypothesis that addictive behavior is driven by reward-seeking and lack of inhibition. Their review leads to a very unsatisfying conclusion:

It is likely that aspects of brain function described by both the impulsivity and reward-deficiency hypotheses contribute to the pathophysiology of addiction.

A more thorough description of the impacts of substance abuse on the brain is available from NIDA. Dr. Nora D. Volkow and her associates produced a review of the neuroscience of drug addiction in 2019 that is fairly comprehensive.

The review starts with the fact that drug use is perceived as rewarding mostly due to “dopamine signaling in the nucleus accumbens.” Chronic drug use results in “neuroadaptations” that can result in addiction “in vulnerable individuals.”

Addiction is fueled, according to the NIDA review, by the yin and yang of the anticipation of use followed by dissatisfaction with the actual high. According to the researchers:

In parallel to the enhanced sensitivity to the expectation of the drug’s rewarding effects (due to conditioning), there is a reduced sensitivity of the dopamine reward circuit to the actual consumption of the reward, which has been observed in drug addicted individuals and interestingly also among some obese individuals who display some phenotypic traits consistent with ‘food addiction.’

Whether a reduced reward response is a predictor of addictive behavior, it most certainly is a result of addictive behavior. Addicts become numb to the ordinary pleasures of life. As the researchers describe it:

Imaging studies have also revealed decreased activation of brain reward regions to receipt of non-drug rewards, such as food, sexual stimuli, or money, in individuals addicted to drugs compared with controls.

As to vulnerability to addiction, the researchers state that “deficits in self control  contribute greatly to an individual’s inability to avoid risky or self-destructive behaviors, resist temptation (such as taking drugs), or delay gratifications.” So how do we spot “deficits in self-control” and is there any way to strengthen them?

Imaging is the answer NIDA offers in their review: “Prospective imaging studies of brain development are increasingly revealing that abnormalities in the PFC [prefrontal cortex] constitute a vulnerability risk for SUD [substance use disorder].” And later they add, “A disrupted connectivity between PFC and striatal regions [is] a consistent finding among individuals addicted to various drug classes.”

As to repairing a deficit in self-control so as to resist addiction or recover from it, NIDA is hopeful for medical intervention, including pharmacology, optics, ultrasound, or other physical measures to repair the reward response and build self-control. There are also techniques such as conditioning, mindfulness, and fasting to restore self-control. And for children, there are games and apps that build self-control.

Written by Steve O’Keefe. First published December 19, 2024.

Sources:

“Imaging brain response to reward in addictive disorders,” Addiction Reviews, January 2011.

“The Neuroscience of Drug Reward and Addiction,” Physiological Reviews, October 2019.

Image Copyright: davdenic, used under Creative Commons license.