It is not uncommon for teenagers as young as 15 to develop psychosis, a psychiatric disease that hits about 1 per cent of the Hong Kong and global populations, according to a University of Hong Kong psychiatrist. Eric Chen Yu-hai said about a third of the 200 new patients seeking treatment for psychosis at Queen Mary Hospital each year were aged between 15 and 18. The youngest patient he had treated was an eight-year-old boy in Britain. Dr Chen acknowledged that some teenage cases could be linked to drug abuse causing brain damage, but said the cause in other young patients remained unclear. The psychiatrist warned that new immigrants' fear of discrimination and the pressure of an urban lifestyle had been identified as possible factors that increased the risk of the disease. Another factor is viral infections in pregnant women, such as influenza, which can increase the risk of psychosis in children by up to 5 per cent. 'But cases involving patients under the age of 15 are very uncommon, so parents should not over-worry,' Dr Chen said. Meanwhile, a study recently released by his team showed psychotic patients who lived with their families received treatment in half the time of those living alone. The study of 131 such patients aged 18 to 55 between 1997 and 2002 showed the time lapse between the onset of psychosis and the first intake of drugs to treat the disease was 816 days for patients who lived alone - compared with 468 for those who lived with their family. For patients with a family history of psychosis, the time lapse was 225 days, compared with 645 for patients without a family history. Dr Chen explained that patients living alone who had other sufferers in the family could help identify their own symptoms earlier. Similarly, the families of those living at home could also detect the symptoms and advise the sufferer to see a doctor. Dr Chen said early diagnosis was important as the condition would deteriorate if treatment was delayed. Common symptoms of psychosis include hallucinations, delusions, paranoia, withdrawal from social networks and disorganised thoughts.