Students sitting Leaving and Junior Cert exams next week need to get as much sleep as they can - up to 10 hours a night if possible - as it will affect how they perform.
The temptation may be to cram and spend extra hours each night studying instead of getting shut-eye.
But researchers from Ghent and KU Leuven Universities in Belgium recently surveyed 621 first-year university students about their sleep habits during exam periods.
The findings show that students who sleep seven hours each night during the exam period did nearly 10pc better than students who got less sleep.
Lucy Wolfe, an Irish sleep expert dealing with teenagers and young adults, highlighted that sleeping habits "have a massive effect on exam performance".
"Very often the inclination is to stay up all night cramming, but this would not be recommended.
"In order to do this, there is an over-reliance on caffeine or fizzy drinks that not only make achieving and maintaining sleep harder - they will also affect the quality of sleep," added Ms Wolfe, who has been dubbed 'The Sleep Fixer'.
She pointed out that the aim is for eight to 10 hours, as this is the recommended amount for those aged 13 to 18 years. "Avoid caffeinated fizzy drink and remember that chocolate has stimulants in it too. Energy drinks also would have a serious health implication, and not just for sleep."
In the month leading up to exams, the number of teenagers who had just five to six hours' sleep a night doubled from 10pc to 20pc, the Belgian study also found, which researchers said was counterproductive. Study co-author Dr Stijn Baert, of Ghent University, said "students who generally get a good night's sleep performed better on exams".