Dabosmita Parial – dabosmita.parial07@gmail.com
August 4th, 2025
Edited by the YNPS Publications Team.
ABSTRACT
Many studies and research have identified that addiction causes lasting changes to the brain structure and function, especially in areas related to impulse and inhibitory control, as well as the prefrontal cortex. This paper reviews a range of research investigating the effect of addiction on the brain’s neural pathways, including those involved in executive functioning, attention and memory. Key results include changes in the size of the hippocampus and reductions in WMD and GMD in the prefrontal cortex. The decrease of CBF to DLPFC and changes in the structure of OFC have also been found. There were also other functional alterations, such as reduced inhibitory control in tasks, as well as emotional regulation. Overall, permanent changes to the brain’s structure and function can be observed by evidence of MRIs and fMRIs along with other cognitive tests.
INTRODUCTION
Addiction can be characterised as a disorder that is chronic and often relapsing due to an uncontrollable and compulsive behavioural activity, even when there are harmful and unhealthy consequences. While addiction is usually associated with drug use, alcohol, and smoking, it is quite possible to be addicted to anything, for example, internet use, shopping, and sex.
It is mainly referred to as a brain disorder as it can cause functional damage to the brain’s neural pathways related to stress, reward, and impulse control. Recent evidence suggests that there have been permanent alterations and abnormalities in the brain caused by addiction, such as reduced activity in the prefrontal cortex and low GMD in the frontal lobe, which affects logical decision-making and other cognitive functions..
METHODOLOGY
This paper presents a literature review of previous research studies. This paper will focus on and analyse the negative effects of addiction on brain structure and function. Sources were selected from PubMed and the National Institute of Health database. The sources were found using the keywords such as “addiction”, “neurological basis”, “neuroscience”, and “effect on brain”. They were used as they provided an overview of the effects seen on the brain as a result of both behavioural and substance addiction. I found some of these sources by going through the references of other literature reviews, such as those describing the effect of drug addiction on the brain. By using the sources they used, I was able to get a clearer understanding of the basis of the evidence used in this research. Most of these research reviews and studies focused on young adults and adults in general, without any specific focus on different sexes, and one focused on adolescent drug abuse.
RESULTS
Effect of substance addiction on adolescents’ brains
In general, changes and abnormalities were observed in the brain structure volume, white matter quantity and activation in certain regions of the brain, even with a very small amount of time, such as 1-2 years of heavy drinking.
Research indicates that adolescent heavy drinkers show decreased memory function alongside low attention spans and a reduction in executive functioning, which involves the ability to remember instructions and handle multiple tasks efficiently. One particular research study, Brown et al, found that even drinkers who had been abstinent for a while had similar results to current drinkers. They recalled 10% less verbal and non-verbal information than controls.
Previously, marijuana was thought to have no long-term effects on the brains of adolescents; however, recent studies have proved otherwise. Findings suggest that adolescents who smoke marijuana perform poorly in tasks related to learning and cognitive flexibility, and working memory.
Furthermore, when the brain structures of these adolescents were examined using MRI, it was found that heavy alcohol drinkers had smaller left hippocampal volumes. This indicates the effect of alcohol on memory function. In another study, where adolescent heavy drinkers were compared to non-drinkers and marijuana users, it was found that the prefrontal volumes were smaller in heavy drinkers compared to controls. Additionally, it was found that female marijuana users have larger prefrontal cortex volume, which may have been linked to poor verbal memory.
During tasks testing inhibition, it was found that marijuana users showed increased brain effort to inhibit responses even after a month of abstinence. It was proven by greater activation in the right dorsolateral prefrontal cortex, a region important for decision making. This result may indicate that their brain had already changed due to regular marijuana use or that the participants had these brain differences before the use of marijuana itself.
→ General impact of substance abuse
Using fMRI, it was found that cocaine users showed less CBF (cerebral blood flow) in the left dACC (dorsal anterior cingulate cortex) and right DLPFC ( dorsolateral prefrontal cortex) during difficult tasks. This implies that with more cocaine use, there was less brain activation. Similarly, men using marijuana were found to have reduced brain activity in key prefrontal regions like DLPFC and ventromedial PFC, which suggests that these men had impaired emotion regulation and control over decision-making. Alongside this, many cigarette smokers who were tested after 12 hours of abstinence showed decreased activation in the right DLPFC during the Stroop task, indicating lower impulse control. This also suggests that the effects do not fully go away with abstinence.
In another similar study comparing the volume of the prefrontal cortex in polysubstance abusers using MRI, it was found that while there was no significant difference in overall brain volume in addicts, the size of their prefrontal and temporal lobes was significantly smaller in substance users, and in the prefrontal lobe, the grey matter volume was comparatively less in both left and right hemispheres of substance addicts.
→ Effect of behavioural addiction
In a research review, scientists have found that the function of the OFC (Orbitofrontal cortex) and other subcortical brain structures, along with neurotransmitters such as serotonin and dopamine, is involved in behaviours such as impulsivity and decision-making. This was mainly identified by using cognitive tasks such as decision-making tasks, which help researchers to observe and learn how the brain works during certain behaviours. This helps us establish the idea that activation in this region of the brain may be reduced for gambling addicts, as Fineberg et al found that both gamblers and alcohol users show increased impulsivity.
Several other studies have found that when people perform inhibitory tasks with neutral and Sexual images Vs. Neutral images, people with high sexual excitability and impulsivity showed worse task performance. This result tells us this demographic had difficulty inhibiting responses after seeing sexual stimuli, which implies that there might be alterations in their neural pathways connected to executive functioning and inhibitory function in the PFC (pre-frontal cortex).
Another review assessing studies related to Internet Gaming Disorder mainly found that there was a reduction in grey matter volume in sections of the brain involved in decision making, behavioural inhibition and emotional regulation. It is also to be noted that reduced WM density was present in the frontal gyrus, insula, amygdala, and anterior cingulate.
Adolescents with IGD had lower diffusion measures in areas associated with emotional regulation, attention, etc. Increased video game play was also associated with delayed development of certain areas of the brain; a few examples include the hippocampus and the OFC A study done on adolescents is Cai et al., which included twenty-seven adolescents, found that IGD participants showed increased volumes of brain regions such as the caudate, which controls cognitive functions such as attention and impulse control, hence the enlargement indicated impairments in those functions. However, it is to be noted that these studies involving adolescents need to be replicated in order to increase reliability.
Conclusion
In conclusion, the main effects of different types of addiction include permanent changes to the structure and functioning of the brain, such as a decrease in volume of regions related to attention and other cognitive functions, such as the hippocampus and the prefrontal cortex. It also alters pathways related to reward processing and inhibitory control, hence making impulse control much more difficult. Lastly, there are considerable changes to the WM and GM density in regions controlling emotion regulation and decision making. More research is still required to develop treatments to prevent these long-term damages and learn how addiction targets changes in certain areas of the brain.
References
Goldstein, R. Z., & Volkow, N. D. (2011). Dysfunction of the prefrontal cortex in addiction: Neuroimaging findings and clinical implications. Nature Reviews Neuroscience, 12(11), 652–669. https://pmc.ncbi.nlm.nih.gov/articles/PMC3462342/#S7
Liu, X., Matochik, J. A., Cadet, J.-L., & London, E. D. (1998). Smaller volume of prefrontal lobe in polysubstance abusers: A magnetic resonance imaging study. Neuropsychopharmacology, 18(3), 243–252. https://www.nature.com/articles/1395124
Love, T., Laier, C., Brand, M., Hatch, L., & Hajela, R. (2015). Neuroscience of Internet pornography addiction: A review and update. Behavioral Sciences, 5(3), 388–433. https://www.mdpi.com/2076-328X/5/3/388
National Institute on Drug Abuse. (2020, July). Drug misuse and addiction. U.S. Department of Health and Human Services. https://nida.nih.gov/publications/drugs-brains-behavior-science-addiction/drug-misuse-addiction
National Health Service. (2024, July 23). Addiction: what is it? NHS. https://www.nhs.uk/live-well/addiction-support/addiction-what-is-it/
Squeglia, L. M., Jacobus, J., & Tapert, S. F. (2009). The influence of substance use on adolescent brain development. Clinical EEG and Neuroscience, 40(1), 31–38. https://pmc.ncbi.nlm.nih.gov/articles/PMC2827693/
Weinstein, A. M. (2017). An update overview on brain imaging studies of Internet Gaming Disorder. Frontiers in Psychiatry, 8, Article 185. https://www.frontiersin.org/journals/psychiatry/articles/10.3389/fpsyt.2017.00185/full
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