It's so bad that seven out of 10 Australian teens are sleep deprived, says Dr Chris Seton, a paediatric and adolescent sleep physician.

Without intervention, they are vulnerable to learning problems, family disharmony, school absenteeism, poor self-esteem, depression and obesity, he says.

Children aged 12 to 18 need an average of nine hours sleep a night.

A good way for parents to tell if they are not getting that is to monitor how late they sleep at weekends, says Dr Seton of the Woolcock Institute of Medical Research.

"It's a red flag if they sleep more than two hours beyond their normal wake-up time."

The institute, which is linked to the University of Sydney, has opened a specialist fortnightly clinic for children with sleeping disorders.

Screen use is the most common problem among teenagers, but they can also suffer from obstructive sleep apnoea, psychological insomnia and a jetlag-type condition known as delayed sleep phasing.

Some children develop delayed sleep phasing at puberty, causing their body clock to go out of sync, causing tiredness and anxiety.

The clinic will provide access to specialists in medical and psychological aspects of sleep as well as doctors who understand allergies and ear, nose and throat conditions.

Dr Seton has also developed a website called Sleepshack, where teenagers can have online consultations with him and a sleep psychologist.

It contains a free section to help with problems related to screen use.AAP