Taking the first step towards better mental health: Reduced daily smartphone use leads to less problematic smartphone use, fear of missing out, depression and dysfunctional emotion regulation.

Problematic smartphone use (PSU), depression and fear have become increasing public mental health issues around the globe. Therefore, it is crucial to investigate behavioral interventions to reduce their occurrence and improve psychotherapeutic diagnostics and treatment. Overall, 194 persons (80.9% women; Mage = 29.33, SDage = 10.44, range: 18-79) from Germany participated in the experimental study. Participants reduced their daily smartphone use time by 60 min over 14 days or continued their use as normal in the control group. Online surveys at six measurement time points (baseline, intermediate, post-intervention, one, three and six months after the intervention) were conducted and results were taken from general linear models. Participants showed significantly less daily smartphone use time, PSU, "fear of missing out" (FOMO), depressive symptoms and emotion regulating reasons of smartphone use six months after the intervention. In conclusion, the reduction of daily smartphone use time can service as a cost-efficient and easily applicable intervention to promote psychological wellbeing, to reduce PSU and prevent psychopathological disorders.