Data Sheet 1_Circulating phospholipid species and internet addiction severity in Japanese adolescents: a pilot lipidomics study.docx

Internet addiction is increasing among adolescents, yet biological markers remain scarce. Lipid metabolism influences neurobehavior, but its association with internet addiction is unclear. Plasma concentrations of 150 phospholipid species from eight classes—phosphatidylinositol (PI), PI3P, PI4P, PI(3,5)P2, PI(4,5)P2, phosphatidylethanolamine (PE), phosphatidylcholine (PC), and PIP3—were quantified in 34 Japanese adolescents (mean ± SD age = 16.4 ± 0.5 y) using targeted LC-MS/MS with isotopic internal standards. Internet addiction severity was assessed by the 20-item Internet Addiction Test (IAT; range 0–100). Associations between lipid species and IAT scores were examined using linear regression adjusted for sex, with false-discovery-rate (FDR) correction for multiple testing. Several PE and PC species showed significant associations with IAT. In particular, PE 36:4 (β = 5.00, 95% CI 1.67–8.33, q = 0.042) and PE 36:2 (β = –1.33, 95% CI –2.29 to –0.38, q = 0.042) were among the strongest indicators. Additional suggestive associations were observed for PE 38:3, PE 40:5, and PC 38:3. Specific circulating PE and PC species are associated with internet addiction severity in Japanese adolescents. These preliminary findings highlight lipid dysregulation as a potential biomarker for problematic internet use and warrant confirmation in larger, longitudinal studies.