ABSTRACTBackground and AimsInternet gaming disorder (IGD) is a relevant psychiatric disorder during adolescence. Excessive digital gaming has been associated with youth mental health problems. Prospective studies combining psychological and biological outcomes in childhood and adolescence are rare.MethodsA sample of n = 178 children was studied at primary school age (M = 7.7 years, t1) and during adolescence (M = 13.3 years, t2). Data was collected in mother‐ (t1, t2) and self‐reports (t2) on screen time, gaming behavior, emotional/behavioral symptoms and biological/psychological stress. Adolescent gamers and nongamers were compared using sex‐controlled (co)variance analyses and correlations with the gaming scores were carried out.ResultsAt t1, there were no differences between adolescent gamers versus nongamers. At t2, self‐reports indicated elevated psychological stress (p = 0.01) and an increase in behavioral symptoms (p = 0.01) in both sexes. Furthermore, gaming girls exhibited a higher prevalence of self‐reported emotional symptoms (p = 0.05); no differences were observed in mother‐reports or hair cortisol concentrations. In the gaming group, more DSM‐5 internet gaming disorder (IGD) symptoms at t2 were associated with higher mother‐rated total symptoms and digital gaming screen time at t1 in boys (p = 0.03/0.04), higher self‐rated psychological stress and more emotional/behavioral/total symptoms in boys (p = 0.002–0.02) and lower hair cortisol concentrations in girls (p = 0.003) at t2.ConclusionThe phenomenon of online gaming in adolescence had no precursors in childhood, while it was associated with current mental health and stress parameters. The extent of gaming, as defined by the DSM‐5 IGD symptoms, was found to be associated with screen time and mental health issues in childhood and adolescence. Consequently, it can be hypothesized that adolescent online gaming is a symptom of earlier as well as a risk factor for current mental health problems during adolescence, with specific consequences for boys and girls.