Social Media Overuse Linked to Stress-Gene Methylation in First Longitudinal Epigenetic Study

What happens to our genes when we cannot stop scrolling? A research team led by Christian Montag of the University of Macau and Simon Sanwald of Ulm University has taken one of the first serious looks at the molecular biology of problematic internet and social media use, and the results hint that the stress system and the brain’s social hormone may both be involved. The study, published in BMC Psychiatry, examined DNA methylation patterns in three candidate genes in depressed patients and healthy controls, tracking them over a two-week treatment period. It is among the first longitudinal epigenetic investigations of internet use disorder tendencies ever conducted, and its findings, while preliminary, open an intriguing window onto how excessive online behavior might be written into our biology.

Internet use disorder, the umbrella term that covers problematic gaming, gambling, and social media overuse, affects roughly seven percent of people worldwide according to meta-analytic estimates. Despite the global debate about the harms of excessive screen time, particularly in children and adolescents, the biological basis of these behaviors remains poorly understood. While the World Health Organization officially recognizes Gaming Disorder and Gambling Disorder, most other forms of problematic internet use have no official diagnostic status, and molecular genetic research on the topic is remarkably scarce. In more than fifteen years of research, only a handful of candidate gene studies have been conducted, and their findings have not replicated well, largely because small samples lacked the statistical power to detect the tiny effects that single genetic variants exert.

This is where epigenetics enters the picture. The epigenome is the layer of molecular regulation where genes and environment meet. Environmental factors, from stress to social connection, can alter gene regulation by changing methylation patterns, the attachment of small methyl groups to DNA bases, most notably in promoter regions that control whether a gene is switched on or off. For the serotonin transporter gene SLC6A4, higher promoter methylation has been associated with lower mRNA levels, meaning the gene produces less of its protein product. This matters for internet use disorder research because preliminary evidence suggests that selective serotonin reuptake inhibitors, which target the serotonin transporter, can reduce symptoms of internet gaming disorder by between roughly 17.6 and 24.0 percent.

The German team chose three genes with strong a priori rationale. Beyond SLC6A4, they examined NR3C1, which codes for the glucocorticoid receptor, a central player in the body’s stress response. Previous work has linked increased NR3C1 methylation to chronic alcohol drinking and to future substance use in adolescents, and since problematic internet use shares features with substance addictions, a connection seemed plausible. The third target was OXT, the gene coding for oxytocin, a hormone central to human sociability. Lower OXT methylation has previously been associated with higher sociability and with depression. Although OXT itself had not been studied in the context of addictive behavior, a recent epigenetic study had implicated the related oxytocin receptor gene OXTR in internet addiction scores.

The study design was ambitious for this field. The researchers recruited 99 inpatients with Major Depressive Disorder at Ulm University’s Department of Psychiatry and Psychotherapy III, ultimately analyzing data from 83 patients alongside 83 matched healthy controls drawn from an initial pool of 169. Diagnosis was made by psychiatrists using the Structured Clinical Interview for DSM-IV, while healthy controls underwent screening interviews to exclude any mental disorder. Participants completed questionnaires measuring generalized internet use tendencies with the short Internet Addiction Test, problematic social media use with the Bergen Social Media Addiction Scale, and perceived social support with the FERUS social support scale. Blood samples were drawn at baseline and again two weeks later, capturing methylation of 13 CpG units in OXT, 27 in SLC6A4, and 16 in NR3C1, alongside mRNA abundance and blood cell composition.

The two-week window was chosen deliberately. Because psychiatric symptoms often improve significantly within the first fourteen days of treatment, the team hypothesized that if methylation change contributes to early treatment success, changes should be observable in relevant target genes over this period. The depressed patients indeed showed a significant reduction in depression severity, measured by the Beck Depression Inventory, over the two weeks, while the healthy controls remained essentially stable. Propensity score matching aligned the groups on age, sex, and alcohol consumption, and the statistical models additionally controlled for nicotine use, body mass index, baseline depression severity, antidepressant dose equivalents, and the abundance of lymphocytes and neutrophilic granulocytes, the most frequent nucleated cells in peripheral blood.

The headline finding concerned NR3C1 in the depressed patients. Methylation at a single CpG site on chromosome 5 was significantly and positively associated with problematic social media use, with generalized internet use disorder tendencies, and specifically with the craving facet of the short Internet Addiction Test, with correlation coefficients between 0.33 and 0.40 that survived false discovery rate correction. Given that NR3C1 governs the glucocorticoid receptor and the body’s response to stress, the authors note that this pattern fits with the idea that excessive internet use, like substance use, may function as a maladaptive compensatory strategy intertwined with the stress system. The result is also consistent with earlier findings linking NR3C1 hypermethylation to alcohol use disorder and adolescent substance use, though other studies, including work on cannabis use disorder, have found no such associations.

The oxytocin results painted a complementary picture. In healthy controls, social support was significantly associated with methylation at a CpG site in the OXT promoter on chromosome 20. More strikingly, across both groups, higher social media addiction tendencies predicted smaller changes in OXT methylation between the two measurement points, suggesting that the quality of one’s social connections, whether online or offline, may be reflected in the methylation dynamics of the oxytocin gene. However, the researchers urge caution: the effect was small, fixed effects in the model explained only about six percent of the variance, and after bootstrapping with 5,000 iterations the confidence interval contained zero, meaning the finding cannot yet be distinguished from chance.

Notably, the serotonin transporter gene yielded no significant associations with internet or social media use tendencies after correction, despite two CpG sites showing correlations with SLC6A4 mRNA abundance in patients. The authors suggest this may partly reflect pharmacological contamination, since antidepressant treatment targeting the serotonin transporter may itself influence methylation at this locus. Most CpG sites across NR3C1 and OXT also showed non-significant correlations, underscoring that any effects, if real, are highly localized and subtle.

The study’s limitations are candidly acknowledged. No participants had an official internet use disorder diagnosis, because none exists beyond gaming and gambling disorder. Self-report questionnaires are vulnerable to social desirability and introspective biases, the two-week observation period may be too short to capture meaningful methylation change, and peripheral blood methylation may not mirror brain methylation, although prior research suggests SLC6A4 blood methylation does relate to brain serotonin synthesis, brain function, and amygdala tissue methylation. Factors such as time of day and fasting state were not controlled. Still, the researchers argue the work matters on three fronts: it provides rare longitudinal methylation data for genes relevant to both depression and internet use disorder, it addresses clinically relevant comorbidity, and it offers a more nuanced biological picture of depressed inpatients. As debates intensify over whether problematic social media use warrants its own diagnosis, this study marks an early but genuinely novel step toward understanding the molecular underpinnings of our relationship with the screen.

Subject of Research: Epigenetic associations between DNA methylation of SLC6A4, NR3C1 and OXT and problematic internet and social media use in depression

Article Title: Epigenetics of generalized internet use disorder including data on overuse of social media: a closer look at the SLC6A4, NR3C1 and OXT genes

Article References: Epigenetics of generalized internet use disorder including data on overuse of social media: a closer look at the SLC6A4, NR3C1 and OXT genes. (n.d.). https://doi.org/10.1186/s12888-026-08743-1

Image Credits: AI Generated

DOI: 10.1186/s12888-026-08743-1

Keywords: epigenetics, DNA methylation, internet use disorder, social media addiction, NR3C1, SLC6A4, OXT, oxytocin, glucocorticoid receptor, major depression, longitudinal study, behavioral addiction