ALTHOUGH many people believe adolescents are too lazy to get out of bed in the morning, there's actually a main contributor to their morning behaviour - a delayed 'body clock' (also known as a delayed circadian rhythm). Teenagers' body clocks the world over want them to fall asleep later and wake up later. And in the most extreme cases, a delayed body clock begins to impact on the teenager's life - especially their schooling. In an earlier randomised controlled trial, where we used a combination of light therapy and cognitive-behaviour therapy, we found 16% of teenagers were not able to attend school because their sleep patterns were so late. And most of the teens enrolled in this trial were frequently late getting to school, and/or had complete days off of school because of their poor sleep. When a teenager's body clock affects them this much, it warrants a diagnosis of Delayed Sleep-Wake Phase Disorder, or DWSPD.

More recently, we ran a new randomised controlled study to test whether light therapy alone could help teenagers with DSWPD sleep better - and we also tested whether the colour of light mattered (i.e., that green light would be more effective than red light). Not only did their sleep improve, but so did their performance on a range of IQ tests, as well as a range of insomnia symptoms.

But given it can be very hard for teenagers to work up the motivation to change their sleep patterns, this time we were also interested in what aspects of their motivation worked for them (or against them). In a newly published study, we share these insights. Many teens present to their first therapy session knowing its important for them to change their sleep pattern; that they need to change it; and they can list plenty of reasons too. But they doubt their ability to change it. Yet at the end of the very first therapy session, when we teach them why their sleep patterns are late, and provide a tailored schedule of light therapy for the upcoming week, it's their desire to change and their confidence to change that eventually predicts how much they will stick to their tailored plan.

What's next? Develop and test techniques that help to raise these teens' confidence in making a change to their sleep pattern. We've already gained insights on how to do this from our work delivering sleep education in high schools. So chances are we can help improve the sleep health of teens who happen to make it school - as well as those that cannot.

And before you say "Just take their bloody phones away from them!" - we're onto that too ... including how to motivate them to put their phone to sleep!