Available data does not show that softer drug laws results in increased adolescent cannabis use, according to a new study.

The publication of the report comes as a State-appointed group here finalises its recommendations to the Government on possible changes to our laws on possession.

The study, conducted by Professor Alex Stevens at the University of Kent, said that currently it was not possible to identify a relationship “in either direction” as a result of reforming drug laws.

His report involved an examination of the data and findings of a landmark 2015 piece of research, which had concluded that liberalisation of drug policy was significantly associated with higher odds of adolescent cannabis use.

That research, conducted by Shi et al, has been cited by several researchers as evidence of such a link and Prof Stevens said the findings were of “high academic and policy interest”.

Prof Stevens, of the School of Social Policy at Kent University, said that a “kind of peace” had broken out in several parts of the world on the so-called “war on drugs”.

In his report, published in the International Journal of Drug Policy, he said countries like Canada, Uruguay, Jamaica, Portugal, the Czech Republic, Spain, Germany, Italy and several US states had reformed laws on cannabis.

“However, little is known about the population-level effects of such legal changes,” said Prof Stevens. “The research that has been done has tended to suggest mixed results.”

He said the Shi et al study looked at data from the WHO Health Behaviour in School-aged Children surveys of 38 countries collected in 2001/02, 2005/06 and 2009/10.

That broke down the countries into four categories: full prohibition, partial prohibition, depenalisation and decriminalisation.

Ireland was one of 18 countries with a full prohibition policy. Some seven countries adopted a partial prohibition response, three had a depenalisation policy and 11 had a decriminalisation approach.

Prof Stevens examined the data and analysis in the Shi et al study and concluded that the association between policy liberalisation and lifetime and past year cannabis use was “statistically non-significant” at the five per cent level of both boys and girls.

“With these models, it is not possible either to confirm or discard a relationship (in either direction) between policy ‘liberalisation’ and adolescent cannabis use,” said Prof Stevens.

He said the approach taken by Shi et al “does not provide robust support to their conclusion”.

He concluded: “Using a larger and more theoretically relevant sample of the HBSC respondents and an improved statistical model shows that the HBSC data do not reveal a statistically significant association between policy ‘liberalisation’ and higher odds of adolescent cannabis use.”

He pointed out that his analysis “cannot demonstrate that there is no casual association” between liberalising drug laws and adolescent cannabis use.

The publication of the report comes as a State working group here is coming to the end of its deliberations on whether or not the Government should change laws for the possession of all drugs for personal use.

The group, whose membership is dominated by high-level State officials, was set up on the back of a recommendation by the Oireachtas justice committee that the Government consider adopting an approach similar to the Portugese model, which involves a non-criminal approach to possession.

The Irish Examiner reported last January that the group had been informed that because the Irish legal system differed from that of Portugal it would be difficult to decriminalise possession – and that one proposal would be to retain criminalisation but introduce a policy of diversion for those caught in possession to the health service and away from the courts.

The group, chaired by Mr Justice Garreth Sheehan, was due to report last December, but was given a three-month extension to finalise their recommendations and draw up their report.