A new study from the University of Kent has found no evidence that teenage cannabis use is lower in countries with tougher policies.

The study, by Alex Stevens, Professor in Criminal Justice in Kent's School for Social Policy, Sociology and Social Research, used data from the World Health Organisation's Health Behaviour in School-aged Children survey. This survey asked over 100,000 teenagers in 38 countries, including the UK, USA, Russia, France, Germany and Canada, about their cannabis use.

Professor Stevens's analysis of the data found no association between a country having a more liberal policy on cannabis use and higher rates of teenage cannabis use. The analysis controlled for differences between the countries, including their national income, and between the teenagers, including their gender, their affluence and psychological problems.

The new study was undertaken in response to a 2015 study that had concluded there was an association between policy liberalisation and a higher likelihood of adolescent cannabis use. This study has been used in the past to justify calls for tougher policies for cannabis use.

However, Professor Stevens found this was based on a misinterpretation of that study's own numerical results. When taking into account the differences in cannabis use between boys and girls in different countries, and using more of the available data, a statistically significant association between policy liberalisation and adolescent cannabis use cannot be found.

Professor Stevens said: 'My new study joins several others which show no evidence of a link between tougher penalties and lower cannabis use. This is useful information for governments as they consider the best way to deal with cannabis. As it is, the harms and costs of imposing criminal convictions on people who use cannabis do not seem to be justified by an effect in reducing cannabis use.'