Data from 6,595 youngsters aged 12 to 15 in the US found those who used social media more heavily were more likely to report issues such as depression, anxiety and loneliness, as well as aggression and anti-social behaviour, than teenagers who did not use social media.
The findings held true even when researchers took into account mental health problems experienced by any young person in the year before they were asked about social media use.
The research, from a team at Johns Hopkins Bloomberg School of Public Health in Maryland, was published in the journal JAMA Psychiatry.
Some previous studies have suggested no link between poorer mental health and screen time.
Dr Rina Dutta, senior clinical lecturer at King’s College London (KCL) and consultant psychiatrist, said: “A major strength of this study compared to previous research is that the researchers took into account mental health problems the young people already had a year prior to the measurement of social media use.
“This largely overcomes the ‘what came first – mental health problem or high social media use?’ question.”
However, she said more research was needed on the issue, including at what points in the day people use social media.
The study looked at two types of behaviours that can indicate mental health problems: Internalising and externalising.
Internalising can involve social withdrawal or difficulty coping with anxiety or depression. Externalising can include aggression or disobeying instructions.
The study found that teenagers who spent three to six hours on social media a day had a 60% increased risk of reporting internalising problems alone, and 78% if they spent more than six hours.
The use of social media for three hours or more was associated with more than double the risk of reporting both internalising and externalising problems.
Lead author Kira Riehm said: “Many existing studies have found a link between digital or social media use and adolescent health, but few look at this association across time.
“Our study shows that teens who report high levels of time spent on social media are more likely to report internalising problems a year later.
“We cannot conclude that social media causes mental health problems, but we do think that less time on social media may be better for teens’ health.”
The study found that fewer than 17% of adolescents did not use social media.
Of those that did, 32% spent less than 30 minutes a day, 31% spent 30 minutes to three hours, 12% spent three to six hours and 8% spent more than six hours per day.
Ms Riehm said: “Social media has the ability to connect adolescents who may be excluded in their daily life.
“We need to find a better way to balance the benefits of social media with possible negative health outcomes.”