A new study is revealing the startling impact smartphones can have when given to children under 13. The study analyzed data from over 2 million participants across 163 countries, focusing on 100,000 young adults from ages 18-24. The data found that people who were given smartphones before 13 suffered from negative mental health later in life. In fact, the younger an individual was when they received a phone, the worse they suffered from such issues as suicidal thoughts, worse emotional regulation, lower self-worth, and detachment from reality. The symptoms were especially bad in girls.

Girls in particular struggled with self-image, self-worth, emotional control, and resilience. Males struggled more with stability, calmness, and empathy. In comparison, girls who received smartphones between the ages of 5 and 6 were 20% more likely than girls who received a smartphone from 13-18 to suffer from suicidal thoughts (48% vs 28% respectively). Boys were 11% more likely (31% younger than 13 vs 20% older). Developed English-speaking nations had the highest rates of mental health impacts, most likely because higher percentages of children receive smartphones before 13 in those regions. “The younger the child gets a smartphone, the more exposure to all this impacts them psychologically and shapes the way they think and view the world,” Tara Thiagarajan, one of the study’s authors, told ABC News.

Access to social media appears to be one of the biggest impacts of mental health, especially given the impact of artificial intelligence (AI) algorithms that specifically target the user. Additionally, children who use social media experience cyberbullying and sleep disruptions, which can impact mental health. Sleep can also be disrupted by such activities as streaming and gaming. Social psychologist Jonathan Haidt has written about the impacts of social media in his book, The Anxious Generation: How the Great Rewiring of Childhood Is Causing an Epidemic of Mental Illness. Haidt has called on keeping children off social media until they are at least 16.

The study authors called on government agencies and stakeholders to create age-related restrictions. “Just as we restrict alcohol, tobacco, and motor vehicle operation to older adolescents and adults based on risk to developing minds and bodies, so too should we restrict smartphones and social media during the critical formative years,” the authors urged. Experts are also calling on parents to take an active role in their children’s smartphone use. Melissa Greenberg, a clinical psychologist at Princeton Psychotherapy Center in New Jersey said parents need to be okay to make changes, even if they’ve already allowed their children to have smartphones. “Don’t be afraid to change course if you feel like what you’ve already done isn’t working for your child or for your family,” she said.