Nagging negative thoughts - and striving for perfection - keep teenagers awake at night, raising their chance of becoming depressed and anxious, a new study shows.

An online study of almost 400 adolescents aged 14 to 20 years confirmed the link, leading sleep researchers at Flinders University to recommend alternative treatments for repetitive negative thinking and perfectionism in dealing with delayed sleep and mental health problems among teenagers.

Professor Michael Gradisar, director of the Child and Adolescent Sleep Clinic at Flinders University, says the study confirmed a link between repeated negative thinking and delayed sleep. This was exacerbated in respondents with perfectionism tendencies.

"Repetitive negative thinking is habit forming and it can significantly contribute to making sleep difficult and causing depressed mood in teenagers, who already like to stay up late at night," Professor Gradisar says.

"This study supports the need to recognise repetitive negative thinking in preventing and treating sleep problems, along with individual differences in perfectionism and mood."

The role of repetitive negative thinking and perfectionism in explaining the link between sleep onset problems and depressed mood has important clinical implications through providing possible treatment targets.

International studies indicates depression affects between 3% and 8% of adolescents. It is often recurring and may continue to develop into more severe depressive disorders during adulthood.

In teenagers, depression can cause poor concentration, a loss of interest in schoolwork, difficulties in peer relationships, and even suicide.

Clinical child psychology Professor Michael Gradisar stresses that sleep plays an important part in preventing and treating depression in teenagers.

He says parents and carers can implement better sleep health by encouraging regular bedtime routines during the school week and weekends, and encouraging mobile phones to be turned off earlier in the evening.

Professor Gradisar says busy lifestyles, stress and screen time makes self-help and accessible resources for better sleep increasingly important.

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The Flinders University sleep clinic has collaborated with national youth mental health services headspace and Orygen to translate evidence-based tools developed from more than a decade of research.

Expertise from Flinders psychology's Child and Adolescent Sleep Clinic have also contributed to new resources for the Sleep Health Foundation and VicHealth.

The new publication, The roles of repetitive negative thinking and perfectionism in explaining the relationship between sleep onset difficulties and depressed mood in adolescents (March 2020) by Iris Huang (BA Hons), Michelle A Short, Kate Bartel, Anne O'Shea, Rachel M Hiller, Nicole Lovato, Gorica Micic, Michael Oliver and Michael Gradisar has been published in Sleep Health (Elsevier) DOI: 10.1016/j.sleh.2019.09.008