Lack of sleep can make already aggressive teenagers more likely to act out

Together with researchers at Flinders University in Australia, she has conducted a study in which 34 female adolescents aged 16 to 18 were fitted with sleep monitors and spent a night in a sleep laboratory.

In the morning, they were woken by a sudden alarm and bright light, which mildly provoked them. Immediately after waking, they were asked to complete a behavioural test in which they had to decide how much wasabi another person would be forced to eat.

“Although this person didn’t actually exist, it was important that the participants believed she did. This is an established method for measuring aggressive behaviour in experimental settings – not just self-reported aggression. We had also measured their usual level of aggression in everyday life beforehand,” explains Serena Bauducco.

Lack of sleep led to aggressive behaviour – but not in everyone

The results showed that shorter sleep strengthens the link between an aggressive disposition and aggressive behaviour. Young people who are usually prone to aggression reacted more aggressively after a shorter night’s sleep. No corresponding effect was observed in young people who are less likely to become aggressive.

“So not everyone becomes more aggressive when they get less sleep, which surprised me a little. It was also unexpected that self-reported sleep quality had no bearing – it was the actual amount of sleep that was decisive,” says Serena Bauducco.

The researchers conclude that sufficient sleep – between 8 and 10 hours in this age group – appears to act as a buffer for young people with an aggressive disposition. When that buffer is weakened, for example after a short night’s sleep, it can become harder to handle provocations calmly.

Easier to talk about sleep than about anger

This knowledge can help young people who struggle to control their impulses or frequently find themselves in conflict with others.

“Our findings confirm the importance of sleep-promoting measures at home and at school, showing that sleep can be a useful starting point when working with young people with behavioural problems. Talking about sleep is often easier than raising more sensitive issues such as anger, impulse control or conflicts,” says Serena Bauducco.

The study involved a single night in the laboratory and only girls, so the results need to be confirmed in larger and more diverse groups. It was conducted in Australia, but the researchers believe a study of Swedish young people would yield the same results.

“The biological mechanisms behind sleep and impulse control are universal. There may, of course, be cultural differences, such as those regarding parental control or lighting conditions, but the fundamental effect – that shorter sleep amplifies aggression in already vulnerable individuals – is likely to be the same,” says Serena Bauducco.