Surveys have revealed a significant decrease in cannabis use by young Australians.

The self-reported lifetime and past-year usage of marijuana for Australians aged 14 to 25 has decreased from 54.8 per cent in 1998 to 31.1 per cent in 2013.

“Those reporting use in the past year also fell from 37.5 per cent in 1998 to 19.1 per cent in 2013,” says University of Queensland researcher Ms Megan Weier.

Males and older respondents were the most likely to report having used cannabis in the past year.

For those who did report using cannabis in the past year, there was a higher likelihood that they would also report poorer physical health and more symptoms of psychological distress.

“Respondents who used cannabis in the previous 12 months were 46 per cent more likely to have a higher rating of psychological distress,” Ms Weier said.

“They were also 43 per cent more likely to rate their health poorly.

“It’s important to note that these statistics may partly be explained by other known associated risk factors such as lower levels of education, other illicit drug use, truancy and financial problems.”

The researchers noted respondents were recruited from home-based environments, excluding data from those without a permanent residence and facing disadvantage.

These methods were consistent across six National Drug Strategy Household Surveys.

The same research centre recently published findings that the number of adolescents (aged 14 to 17) identifying as weekly alcohol drinkers dropped from 20.7 per cent to 5.1 per cent from 1998 to 2013.

They have also produced reports estimating the number of methamphetamine users in Australia rose by more than 170,000 between 2009 and 2015, to a total of 270,000 users nationwide (of all ages).

Another report found methamphetamine residue from the sewers of a Queensland city had multiplied almost five times between 2009 and 2015.