THE number of schoolgirls and elderly people killing themselves has increased dramatically over the past 15 years, according to a study to be released today. Detailed figures were not available last night, but the study will show that while the total number of suicides has not risen steeply, the composition by age group, marital status and occupation has changed sharply. The study - Statistical Analysis of Suicide in Hong Kong - says the retired, unemployed and housewives are most likely to commit suicide. It also reveals that elderly people are the highest risk group, especially those on social security. It concludes that the more that people have to rely on welfare services, the more likely they are to commit suicide. The report, by a senior lecturer at the University of Hong Kong's Statistics Department, Dr Paul Yip Siu-fai, said summer was the peak season for suicide, supposedly because people became more emotional when the weather was hot. The study aims to examine the trends of suicide in Hong Kong over the past 15 years and identify high risk groups.