Teenagers who engage with social media during the night could be damaging their sleep and increasing their risk of depression and anxiety, research shows.

More than 460 teenagers at a secondary school in Scotland were questioned about their general social media habits, and in particular their night-time use of sites such as Facebook and Twitter, as part of the study by Glasgow University.

It found that while overall use of social media affects the quality of sleep, those who log on at night to respond to alerts are particularly affected. It remains unclear, however, whether it is social media that is damaging sleep, or whether teenagers turn to social media because they can’t sleep for some other reason.

Dr Heather Cleland Woods said her study had found that children as young as 11 were on Facebook and Twitter and using them considerably. Some pupils at the Glasgow school were using multiple devices – a phone and a tablet for example – to view multiple sites simultaneously and were on them “into the early hours of the morning”.

Cleland Woods, who presented the paper at a British Psychological Society conference in Manchester on Friday, said: “Adolescence can be a period of increased vulnerability for the onset of depression and anxiety, and poor sleep quality may contribute to this.

“It is important that we understand how social media use relates to these. Evidence is increasingly supporting a link between social media use and wellbeing, particularly during adolescence, but the causes of this are unclear.”

She continued: “While overall social media use impacts on sleep quality, those who log on at night appear to be particularly affected. This may be mostly true of individuals who are highly emotionally invested. This means we have to think about how our kids use social media, in relation to time for switching off.”

Cleland Woods, a mother of two whose background is in sleep research, posed the idea of a “digital sunset”: in the same way that the sun sets a couple of hours before bed, we do the same with our digital devices before bedtime to potentially improve sleep.

As well as being asked about their social media habits, the pupils, aged between 11 and 17, were also asked to respond to a questionnaire which measured sleep quality, self-esteem, anxiety and depression. They were also asked about their emotional investment in social media, the pressure they felt to be available 24/7, and the resulting anxiety if they did not respond immediately to texts or posts.

Preliminary analysis of the research showed overall social media use, and specifically night-time use, was related to poorer sleep quality, lower self-esteem and higher levels of anxiety and depression. A pronounced emotional investment in social media had a similar effect.

Separately, a study of teenage stress commissioned by the National Citizen’s Service youth programme suggests that girls seek comfort from social media when they are anxious and worried.

The survey of 1,000 12-18-year-olds found that nine out of 10 teenage girls have experienced stress in the past year, with seven in 10 cases leading to symptoms of stress-related illnesses.

Rather than talking to their parents, girls are more likely to turn to social media, distracting themselves from the pressure they’re under by Snapchatting friends or browsing Facebook.

The survey suggests that girls are likely to experience stress more frequently than boys, and more often than the average adult, with girls feeling stressed an average of twice a week.

The cause of stress, the survey suggests, is increasingly the anxiety of making important life decisions, with many teenagers suffering from decision paralysis. It found the top three sources of stress for girls were exam results (57%), making decisions about the future (37%) and arguments with friends (36%).

Lucie Russell, campaigns director at the youth mental health charity Young Minds, said: “We should not underestimate the huge amount of pressure young people are facing, especially at this time of year which brings the uncertainties that come with a new academic year.

“Not only has social media added new complexities to their daily lives, but looming, uncertain futures just add to this stress. We need to ensure young people are equipped with the skills to deal with these pressures and to navigate positive paths into adulthood.”