Sleep doctors say many people who are diagnosed with insomnia are actually suffering a condition called delayed sleep phase disorder.
Physicians say up to 15 per cent of people who are told they have insomnia actually have the disorder, which makes it very hard for people to fall to sleep at night and difficult to get up in the morning.
Professor Ron Grunstein from the Woolcock Institute in Sydney says it is difficult to diagnose delayed sleep phase disorder.
"Most people who have it don't know they have a disorder," he said.
"They just think they have trouble getting off to sleep and trouble waking up."
Professor Grunstein says not going to bed before 2am or 3am is common in patients with the condition.
"They will sleep quite soundly but they are unable to get out of bed the next day," he said.
Sydney medical student Michelle Emerson, 25, says she realised she had delayed sleep phase disorder while listening to a university lecture on sleep disorders.
"If ever I have to wake up at what most people would consider a normal time, I'm ridiculously tired and if I could keep pressing the snooze button, I would," she said.
Her ideal bed time is around midnight or even later, but she says that is not conducive to her lifestyle and study.
Doctors are at a loss to explain what causes the disorder, however, they suspect it is a dysfunction of the body's internal clock which tells the body when to go to sleep and when to wake up.
They believe the hormone melatonin - which controls the body clock - may be involved.
Researchers at Sydney's Woolcock Institute are running one of the first trials into delayed sleep phase disorder.
Along with other sites, they will recruit 320 patients with the condition with 160 people treated with melatonin while the rest will be given a placebo.
Professor Grunstein says melatonin has been used on a trial-and-error basis for people with the disorder.
"But there has never been a randomised trial and the purpose of this study is to prove whether melatonin works," he said.
Melatonin helps people get to sleep earlier and also wake up earlier.
"That's helpful because when you wake up earlier, you get more sunlight which normalises body rhythms and circadian rhythms," Professor Grunstein says.
"The drug is already approved for use by doctors, so if it works, people can easily access it."
Researchers are also looking at potential genes involved with delayed sleep phase disorder, although doctors say little is known about which genes might play a role in the condition.
Scientists will begin to look for different genetic markers.
In the future, patients with delayed sleep phase disorder could find the most effective treatments based on their genetic makeup.
Researchers in Sydney, Melbourne and Adelaide are looking for more volunteers for the study.