A new report has revealed a massive decrease in the number of youths and young adults who have used cannabis.

The report, by the University of Queensland’s Centre for Youth Substance Abuse Research, relied on surveys of people aged between 14 and 25.

In 1998, 54.8 per cent of respondents said they had used cannabis at least once in their lifetime.

The same survey was repeated every three years. In 2013, 31.1 per cent of respondents said they had used cannabis.

Lead researcher Megan Weier said it was difficult to determine a cause for the decrease.

“There was a significant decrease of young people reporting they had used cannabis even once in their lifetime,” Ms Weier said.

“Those reporting use in the past year also fell from 37.5 per cent in 1998 to 19.1 per cent in 2013.”

Ms Weier said she believed perceptions about the drug had changed during the 15 years of the study.

“I think the increasing prevalence and range of things like party drugs probably means that cannabis is a less attractive option,” she said.

The report also considered physical and mental health factors among those who had admitted using cannabis in the past twelve months.

“They were more likely to self rate their physical health as being worse and they were also more likely to have higher depressive symptomatology, ” she said.

The decrease in the number of people using cannabis was seen in both males and females. But males more commonly reported cannabis use in the past year.