DSPS, or 'Delayed Sleep Phase Syndrome', usually occurs after adolescence or late childhood. It is also known as phase lag syndrome
What is it?
This syndrome is one of many types of insomnia and usually occurs after a lengthy period of late-night parties and studying/coding/hacking sessions. Even after a you return to a normal day schedule you may find you're unable to sleep at normal hours. The problem is that the major sleep episode has shifted, which leads to complaints of insomnia, being unable to sleep or wake up when you want to. Scientifically: the syndrome is a shift in the circadian rythm
Patients usually fall asleep after 2am, have trouble or unable to wake up during the work/school weeks and wake up late (10am to 3pm) in the weekends. They find ordinary methods like sleeping pills and going to bed early have little or no effect at all. They usually think of themselves as night-people.
There are some known treatments, but success varies. These are mainly chronotherapy, bright light therapy and some natural medications like melatonine. Improving sleeping hygiene (clean room, no background sounds except white noise etc) is also reported to be effective in some cases.
DSPS can be diagnosed if this pattern persists over three months and the major sleep episode has shifted over 2 hours a day. But is rarely diagnosed for people of 30 years of age
Just like with other types of insomnia about 50% of the patients suffer from psychiatric problems like depression.
Thanks to wertperch and Lord Brawl for their help and suggestions | 
