Gaming addiction has recently become classified by DSM-5, ICD-11, and other International systems for disease classification as an emerging mental disorder. The DSM-5 defines IGD as compulsive gaming, “to the exclusion of other interests, and their persistent and recurrent online activity results in clinically significant impairment or distress” (DSM-5 appendix; section III, emerging disorders). Similar to substance abuse disorders, Internet Gaming Disorder interferes with aspects of daily life, such as academic performance and interpersonal relationships. In fact, several cross-sectional studies have shown overlap in brain structural alterations between subjects with gaming addiction and those with substance use disorders (Koob & Volkow 2010; Goldestine & Volkow 2011; Park, Han & Roh 2016). Both groups showed a reduced gray matter volume in the orbitofrontal cortex, which contributes to value-based decision making and inhibitory control. However, it is difficult to determine the causal relationship from cross-sectional studies. Does reduced gray matter volume in the orbitofrontal cortex predispose individuals for addictive behaviors or does the structural alteration result from experience?
Feng Zhou and his team attempt to tackle this question by conducting a longitudinal study on individuals never exposed to World of Warcraft, a popular MMORPG with a recognized addictive potential. They recruited 87 WoW-naive non-gamers, which all have a healthy level of gray matter volume in the orbitofrontal cortex compared to excessive WoW users. They then randomly split the participants into two groups. One group was assigned to a 6-week period of daily WoW gaming (minimum play of 1 hour per day) while the control group did no gaming. Internet gaming addiction score as measured by a validated questionnaire (Lemmens Valkenburg and Peter 2009) and brain structure were recorded prior and after the 6 week regime.
Despite the relatively short timespan, the results show a significant increase in gaming addiction score for the experimental group and a significant decrease of gray matter volume in their orbitofrontal cortex. On the other hand, no significant change was observed in the control group. The negative correlation between gray matter volume and addiction score agrees with previous cross sectional studies. More importantly, the longitudinal study shows that the gray matter loss in the orbitofrontal cortex is a direct consequence of excessive exposure to gaming, which adds support to the theory that gaming addiction is experience-driven rather than predisposed.
Due to similarity in core symptoms and pathological development between substance abuse disorder and Internet Gaming Disorder, Zhou claims that it is reasonable to generalize the result of his longitudinal study to substance addiction. If so, this study might be the first direct evidence that addiction is experience driven, potentially undermining the role of genetic factors. Although later studies confirmed gray matter differences among non-gamers and those with problematic usage, Zhou’s hypothesis that substance addiction is experience driven is not supported by current literature. Zhou and his team may need more evidence to make such a generalization.
Zhou, F., Montag, C., Sariyska, R., Lachmann, B., Reuter, M., Weber, B., Trautner, P., Kendrick, K. M., Markett, S., & Becker, B. (2017). Orbitofrontal gray matter deficits as marker of Internet gaming disorder: converging evidence from a cross-sectional and prospective longitudinal design. Addiction Biology, 24(1), 100–109. https://doi.org/10.1111/adb.12570
Koob, G. F., & Volkow, N. D. (2010). Neurocircuitry of Addiction. Neuropsychopharmacology, 35(1), 217–238. https://doi.org/10.1038/npp.2009.110
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://doi.org/10.1038/nrn3119
Park, B., Han, D. H., & Roh, S. (2016). Neurobiological findings related to Internet use disorders. Psychiatry and Clinical Neurosciences, 71(7), 467–478. https://doi.org/10.1111/pcn.12422
Lemmens, J. S., Valkenburg, P. M., & Peter, J. (2009). Development and Validation of a Game Addiction Scale for Adolescents. Media Psychology, 12(1), 77–95. https://doi.org/10.1080/15213260802669458