Effectiveness of a residential treatment camp for adolescents with problematic Internet use in Japan: A 3-month follow-up pilot controlled study

• Problematic Internet use (PIU) is prevalent in adolescents. • This study evaluated the effect of a residential treatment camp on adolescent PIU. • Internet addiction reduced significantly more in the intervention group. • Adolescents’ mental health and parental behavior significantly improved. • Residential treatment camps may effectively reduce adolescents’ PIU. Problematic Internet use (PIU) is a public health concern in children and adolescents and is associated with physical (e.g., musculoskeletal pain, headache) and mental health problems (e.g., depression, emotional instability). Kagawa Prefecture in Japan introduced a residential treatment camp for adolescent PIU in 2022; however, previous studies on its effectiveness lacked control groups and longitudinal follow-ups. This study evaluated the short-term effects of the treatment camp on Internet addiction severity and mental health indicators using a non-randomized controlled design. This pilot non-randomized controlled study was conducted between July and November 2024, with grade 5–9 students and their parents. The intervention group ( n = 22) attended a 7-day residential camp, whereas the control group ( n = 106) did not. Baseline assessments were conducted in July or August, and follow-up surveys three months post intervention. Students’ Internet addiction, attachment style, mental health, self-efficacy, and lifestyle habits were measured. Parents’ mental health and parenting styles were also measured. Intervention-group students had higher Internet addiction and mental health scores than control-group students at baseline. Post-intervention, intervention-group students showed greater improvements in Internet addiction (Δmedian = − 9.5 vs. − 2.0) and mental health (Δmedian = − 4 vs. 0), while intervention-group parents demonstrated a greater reduction in negative parenting behaviors (Δmedian = − 6 vs. 0). This pilot non-randomized controlled study suggests short-term improvements in camp attendees’ IAT scores and depressive symptoms at 3-month follow-up. A 12-month follow-up is planned to evaluate the longer-term sustainability of these findings.