AN ''EPIDEMIC of narcissism'' has swept across the student population in the past 30 years, a US expert will tell a conference on personality disorders in Melbourne today.

Jean Twenge, professor of psychology at San Diego State University, said a study she conducted of 16,000 university students across the US showed 30 per cent were narcissistic in psychological tests, compared with 15 per cent in 1982. ''They are all 18 and 19-year-olds, so this is clearly a generational shift,'' she said.

Professor Twenge said the finding built on another study based on interviews with 35,000 people of varying ages, who were asked if they had ever had symptoms of narcissism.

''Usually the oldest people have the highest rates, because they have lived for more years, but this data showed the opposite,'' she said. Only 3 per cent of those over 65 had had symptoms, but for people in their 20s it was 10 per cent.