Experiment shows time alone heightens ‘threat alert’ in teenagers—even when using social media

People in their late teens experience an increased sensitivity to threats after just a few hours left in a room on their own—an effect that endures even if they are interacting online with friends and family.

This is according to the latest findings from a cognitive neuroscience experiment conducted at the University of Cambridge, which saw 40 young people aged 16–19 undergo testing before and after several hours alone—both with and without their smartphones.

Many countries have declared an epidemic of loneliness. The researchers set out to “induce” loneliness in teenagers and study the effects through a series of tests, from a Pavlovian task to electrodes that measure sweat.

Scientists found that periods of isolation, including those in which participants could use their phones, led to an increased threat response—the sensing of and reacting to potential dangers. This alertness can cause people to feel anxious and uneasy.

The authors of the study say that isolation and loneliness might lead to excessive “threat vigilance,” even when plugged in online, which could negatively impact adolescent mental health over time.

They say it could contribute to the persistent and exaggerated fear responses typical of anxiety disorders on the rise among young people around the world.

While previous studies show isolation leads to anxious behavior and threat responses in rodents, this is believed to be the first study to demonstrate these effects through experiments involving humans.

The findings are published in the journal Royal Society Open Science.

“We detected signs of heightened threat vigilance after a few hours of isolation, even when the adolescents had been connected through smartphones and social media,” said Emily Towner, study lead author from Cambridge’s Department of Psychology.

“This alertness to perceived threats might be the same mechanism that leads to the excessive worry and inability to feel safe which characterizes anxiety,” said Towner, a Gates Cambridge Scholar.

“It makes evolutionary sense that being alone increases our vigilance to potential threats. These threat response mechanisms undergo a lot of changes in adolescence, a stage of life marked by increasing independence and social sensitivity.”

“Our experiment suggests that periods of isolation in adolescents might increase their vulnerability to the development of anxiety, even when they are connected virtually.”

Researchers recruited young people from the local area in Cambridge, UK, conducting extensive screening to create a pool of 18 boys and 22 girls who had good social connections and no history of mental health issues.

Participants were given initial tests and questionnaires to establish a “baseline.” These included the Pavlovian threat test, in which they were shown a series of shapes on a screen, one of which was paired with a harsh noise played through headphones, so the shape became associated with a feeling of apprehension.

Electrodes attached to fingers monitored “electrodermal activity”—a physiological marker of stress—throughout this test.

Each participant returned for two separate stints of around four hours isolated in a room in Cambridge University’s Psychology Department, after which the tests were completed again. There was around a month, on average, between sessions.

All participants underwent two isolation sessions. One was spent with a few puzzles to pass the time, but no connection to the outside world. For the other, participants were allowed smartphones and given wi-fi codes, as well as music and novels. The only major rule in both sessions was they had to stay awake.

“We set out to replicate behavior in humans that previous animal studies had found after isolation,” said Towner. “We wanted to know about the experience of loneliness, and you can’t ask animals how lonely they feel.”

Self-reported loneliness increased from baseline after both sessions. It was lower on average after isolation with social media, compared to full isolation.

However, participants found the threat cue—the shape paired with a jarring sound—more anxiety-inducing and unpleasant after both isolation sessions, with electrodes also measuring elevated stress activity.

On average across the study, threat responses were 70% higher after the isolation sessions compared to the baseline, regardless of whether participants had been interacting digitally.

“Although virtual social interactions helped our participants feel less lonely compared to total isolation, their heightened threat response remained,” said Towner.

Previous studies have found a link between chronic loneliness and alertness to threats. The latest findings support the idea that social isolation may directly contribute to heightened fear responses, say researchers.

Dr. Livia Tomova, co-senior author and lecturer in Psychology at Cardiff University, who conducted the work while at Cambridge, added, “Loneliness among adolescents around the world has nearly doubled in recent years. The need for social interaction is especially intense during adolescence, but it is not clear whether online socializing can fulfill this need.

“This study has shown that digital interactions might not mitigate some of the deep-rooted effects that isolation appears to have on teenagers.”