As children become teenagers, it’s very common for some to become night owls. They prefer to stay up late and sleep in, despite school, work or university schedules not catering to these preferences. But what are the implications of this? And why do some people continue to stay up into the night, while others revert to a morning-based schedule? An international team of researchers, including from the University of Melbourne and Monash, have conducted a longitudinal study looking at how morning or evening preferences relate to psychological and developmental conditions.
The researchers followed more than 200 adolescents from Melbourne and assessed them each at four different time points between 2004 and 2011, when they were roughly at the ages of 12, 15, 17 and 19. At each of these check ins, the adolescents completed questionnaires asking for self-reports of depression and anxiety (“internalising symptoms”) and “externalising symptoms” (such as aggression, defiance and vandalism). They also completed quizzes assessing their morning-evening preference and how far through puberty they were. Their parents or guardians also filled in questionnaires about any externalising symptoms they had seen. Notably, these individuals had all been screened for things like learning disabilities, chronic medical issues, head injuries, or substance use.
The research found that there was a significant increase in an evening preference through adolescence, and that this did not seem to occur in a linear way, with a greater shift happening between the ages of 12 and 15. They found that on an individual level, a change to an evening preference predicted a higher chance of having externalising symptoms at age 19 – that is, the change was the predictive factor, rather than the evening preference itself. They didn’t find an association between morning-evening preference and internalising symptoms (like mood disorders), which contrasts the findings of some other, less long-running research in the same area.
So how worrying is a change in sleep pattern during adolescence? This research doesn’t account for the full picture, as there are many other factors associated both with changing sleep patterns and the behavioural and psychological conditions that might emerge during this time. Changes in sleep can be completely normal at various stages in life. The research adds to our understanding of the complexity and importance of sleep on our health and wellbeing and is especially valuable given the length of time the adolescents were followed.
