ADHD and Addiction: Is There a Dopamine-Related Link?

 Amrita Rehal

Addiction has affected people and destroyed lives for as long as drugs of abuse have been around. In the past, there have been many theories to try to solve the mystery as to why drug addiction occurs in the first place and how drugs can take such a strong hold on a person, to the extent that they will even neglect biologically necessary processes in favor of their drug of abuse. There have been great leaps made in this area of research in recent years that have helped shed light on the underlying neural mechanisms of addiction. Further, the link between certain neurodevelopmental disorders, such as attention deficit hyperactivity disorder (ADHD) and addiction has also been studied greatly in recent years.

The underlying mechanisms of addiction have been elucidated using animal models of drug addiction.¹ There is a theory known as the “incentive-sensitization theory” of drug addiction that postulates that the characteristic that makes a substance highly addictive has to do with its ability to enhance the transmission of the neurotransmitter dopamine in the mesocorticolimbic system of the brain.² The result of this enhanced transmission within dopamine circuitry is an increased amount of dopamine in the frontal areas of the brain, especially in the nucleus accumbens area. This results in an increased motivation and liking of the drug and all associations with it that causes that enhancement.¹ Another side effect of repeated drug use appears to be a sensitization of these neural circuits, which results in an increased amount of sensitivity of the brain and its dopamine circuitry to the drug of abuse as well as associated stimuli. The result of these processes, in addition to associative learning, is intense drug craving, drug seeking behavior, and prolonged drug use, even despite very negative side effects of drug use.

Great work is currently being done on these mechanisms of drug addiction, such as that of Dr. Stephan Steidl at Loyola University Chicago’s Department of Psychology. A recent publication from his team details the importance of the ventral tegmental area, and specifically glutamatergic signaling in this reward pathway of the brain, in the development of drug sensitization, utilizing cocaine specifically, which is a very common drug of abuse in the United States.² Utilizing a mouse model for addiction, Steidl and colleagues determined that the laterodorsal tegmental nucleus is an important source of this glutamate for cocaine sensitization, as it results in an increase in glutamatergic plasticity. This is relevant because the laterodorsal tegmental nucleus is vital in regulating the activity of dopamine-producing neurons in the brain that are critical to the development of drug addiction.

Recent news articles, such as the one hyperlinked here, have claimed that there are links between ADHD and the development of drug addiction, stating that nearly a quarter of individuals with a substance use disorder also have ADHD.³ The author of this article cites a dysfunction in normal dopamine circuitry as a potential cause for an increased prevalence of substance use disorder in individuals who have an ADHD diagnosis. A link may reside here in the dopamine transfer deficit hypothesis of ADHD.⁴ This theory has to do with the fact that in normal individuals, when a reward is received, the brain’s dopamine systems will wire so that a rewarding feeling is not only felt upon the reception of the reward, but also from cues that predict the reward. According to the dopamine transfer deficit hypothesis, the brains of individuals with ADHD do not have this response, and thus, they have an altered functioning of dopamine that makes it so they do not experience a normal dopamine response to a delayed reward. This has been confirmed using fMRI studies that show dampened activation in the ventral striatum during reward anticipation as compared to controls.⁵ A recent study evaluating individuals with ADHD and crack-cocaine addiction found that individuals with an ADHD diagnosis were more impulsive.⁶ The increased impulsivity of individuals with ADHD has been proposed as a possible reason as to why individuals with ADHD have a high prevalence of substance use disorders, as they are more likely to try the substances in the first place. There could be many mechanisms at play that may predispose individuals with ADHD to drug addiction and substance use disorder, and further research in this area will help elucidate these mechanisms further to aide in our understanding of this comorbidity.

1. Robinson, T. E., & Berridge, K. C. (1993). The neural basis of drug craving: an incentive-sensitization theory of addiction. Brain research reviews, 18(3), 247-291.

2. Puranik, A., Buie, N., Arizanovska, D., Vezina, P., & Steidl, S. (2022). Glutamate inputs from the laterodorsal tegmental nucleus to the ventral tegmental area are essential for the induction of cocaine sensitization in male mice. Psychopharmacology, 239(10), 3263-3276.

3. Sherrell, Z. (2022, May 27). Cocaine and ADHD: Everything you should know. Medical News Today. Retrieved May 3, 2023, from https://www.medicalnewstoday.com/articles/cocaine-and-adhd

4. Tripp, G., & Wickens, J. R. (2009). Neurobiology of ADHD. Neuropharmacology, 57(7-8), 579-589.

5. Plichta, M. M., Vasic, N., Wolf, R. C., Lesch, K. P., Brummer, D., Jacob, C., ... & Grön, G. (2009). Neural hyporesponsiveness and hyperresponsiveness during immediate and delayed reward processing in adult attention-deficit/hyperactivity disorder. Biological psychiatry, 65(1), 7-14.

6. Fond, G., El-Maamar, M., Korchia, T., Richieri, R., Lacoste, J., Boyer, L., & Lancon, C. (2022). ADHD and addictive behavior in crack-cocaine users. L'encephale.