Parents should worry less about the amount of time their children spend on social media during the day and instead make sure their offspring get enough sleep and discuss negative online experiences, researchers say.

A study suggests that while frequent use of social media does appear to be linked to poorer mental health, the effects are not direct. Instead it suggests such links might be down to social media use displacing other activities, such as sleep, or that it opens the door to cyberbullying.

Prof Russell Viner, a co-author of the study, from the UCL Great Ormond Street institute of child health, said: “While we obsess a lot about social media, how much do we obsess about how much our young people sleep? Not very much – but it is a more important factor, actually, in determining their mental health.”

The team say one approach is for parents to keep phones out of children’s bedrooms, adding that teenagers need up to 10 hours’ sleep a night.

Dr Dasha Nicholls from Imperial College London, a co-author of the research, said adults should ask children about whether they were being bullied online. She said: “Parents and others need to know what their young people’s social environment is online as much as they do in the real world.”

But the team say further research into the effects of social media is needed, adding that insights from companies such as Facebook could prove valuable if they were made available.

With half of all mental illnesses starting by age 14, the influence of social media has been in the spotlight. While some have suggested the rise of sites and apps such as Twitter, Facebook and Snapchat could have a negative impact on young people’s health, others have cited positive effects, including connecting young people and boosting support networks. A study published this year by researchers in Oxford suggested the use of social media by children has very little impact on their levels of life satisfaction.

Writing in the Lancet Child and Adolescent Health journal, Viner and colleagues report how they analysed data collected from a series of surveys on how often teenagers used platforms such as Twitter, Instagram and Snapchat. The first was carried out in 2013 among 13- to 14-year-olds across 886 schools in England, and participants were interviewed again in the two years that followed, with 9,797 participants during the final year.

Mental health was assessed through a questionnaire in the second year of the study, revealing 19% of teens had high scores for psychological distress, with such problems more common in girls than boys.

For both boys and girls, having a high score for psychological distress was more likely among those who checked social media more than three times a day, compared with just once a day. However, after taking into account a range of factors including school type, the team then looked at the degree to which that link could be explained by indirect effects.

Viner said: “When you account for cyberbullying, physical activity and sleep, the effect of social media in girls washes out completely.” He said cyberbullying and lack of sleep had the biggest influence.

The study found the same trio of factors explained much less of the link in boys. Viner said it was likely other indirect effects were at play, as it was unlikely a direct effect would only be seen in one gender.

Nicholls said it might be that cyberbullying was less common, or less stressful, for boys than girls.

The study has limitations, including that it is based on self-report, and classes “very frequent use” of social media at more than three times a day, whereas many people access social media far more often. It also only measures mental health and wellbeing at certain points in time.

Amy Orben, a co-author of the earlier Oxford study, said the latest research could not rule out reverse causation, ie that those with poorer mental health or wellbeing used social media more often, while it only looked at frequency of social media use rather than how long children spent on it or what they were looking at.

Tom Madders, the campaigns director of the charity YoungMinds, said the study highlighted the importance of educating children about how to use social media in a positive way.

He said: “Social media can help young people express themselves, connect with friends and find support, but it can also intensify some of the hardest parts of growing up.” But, he added, the charity recognised the problems flagged in the new study.

Madders said: “We often hear from young people about the devastating effects of online bullying, and about how easy it is to find distressing content. As this report suggests, frequent social media use can also affect sleep, which can have a knock-on effect on mental health.”