A new, large-scale study published in the Journal of Human Development and Capabilities reveals how smartphone ownership in childhood may be derailing young people’s mental health.

The study included data from more than 100,000 18- to 24-year-olds living around the globe. Owning a smartphone before the age of 13 was associated with poorer mental health, including diminished self-image, self-worth, and emotional resilience. Additional symptoms included increased aggression toward others, reduced empathy, hallucinations, and feeling detached from reality.