Adolescents who have insomnia are more likely to drink alcohol, smoke and use illicit drugs, and have double the risk of developing mental health problems as they get older, a new study suggests.

"The current study suggests adolescents with insomnia are more prone to developing mental disorders, specifically depression," said the study's lead author Brandy M. Roane, a doctoral student at the University of North Texas.

The study was published Oct. 1 in the journal Sleep.

Baseline study data was collected in 1994 and 1995 from interviews of almost 4,500 adolescents aged 12 to 18 in grades 7 to 12. A followup study between 2000 and 2001 looked at almost 3,600 young adults aged 18 to 25.

Adolescents who said they had trouble falling asleep every day or almost every day were classified as having insomnia. More than nine per cent of the young people who took part reported having trouble sleeping.

The study results indicated that those who reported insomnia symptoms were 2.3 times more likely to develop depression in early adulthood than adolescents without symptoms. Excluding participants who already experienced depression and thoughts of suicide or suicide attempts, the insomnia group also had a greater risk of developing new incidents of these problems.

The study suggests that insomnia not only increases the risk of developing of mental health problems, but also their severity.

Specifically, 54 per cent of the group with sleep problems reported depression, compared to about 32 per cent of those who slept well.

One quarter of those with insomnia said they had thoughts of suicide, compared to 11 per cent in the group that slept well.

Ten per cent of those who slept poorly said they had attempted suicide, compared to three per cent of those slept well.

The study found that the group that reported sleeplessness was more likely to use alcohol, cannabis, and non-cannabis drugs. Almost 33 per cent of the group reporting insomnia reported consumption of alcohol, versus 22 per cent in the group that reported no sleep problems. About 18 per cent of the insomnia group reported marijuana use, compared to 11 per cent in the group that slept well.

Authors of the study acknowledge that the study had limitations which included the lack of a thorough history of sleep problems in the participants, and knowledge of participants' existing medical conditions that might cause insomnia.