Legalising marijuana increases its use, new research reveals.

In Colorado and Washington, the first US states to legalise the drug for recreational purposes, its use has remained consistently high among teenagers but increased substantially in those aged over 25, a study found.

While in Uruguay, which was the first country to legalise cannabis nationwide, 'all indicators of use have risen', the research adds.

In the US, legalisations have significantly increased the number of life-threatening cannabis poisoning cases and have done nothing to ease drug trafficking, the study found.

This comes after campaigners frequently argue marijuana is sufficiently safe to be made broadly legal, adding this may even reduce its use due to people being less inclined to take the drug out of rebellion.

Legalising marijuana increases its use, particularly among those aged over 25, a report finds

TEENAGERS WHO INCREASE THEIR MARIJUANA USE WITH AGE ARE AT GREATER RISK OF DEPRESSION Teenagers who increase their marijuana use with age have a greater risk of depression, an inability to experience pleasure and poor educational achievements in later life, research revealed in July. Men who infrequently use cannabis at age 15 but dramatically increase their use up to 19 years old, are more at risk than those who consistently take the drug throughout their teens, a study found. Lead author Dr Erika Forbes from the University of Pittsburgh, said: 'We expected to see that the young men who had a high, consistent level of marijuana use would have differences in brain function. 'However, it turned out that those who had an increasing pattern of use over their teens had the biggest differences. 'Even though most people think marijuana isn't harmful, it may have severe consequences for some people's functioning, education and mood.' Advertisement

How the research was carried out

The researchers from France's National Institute of Higher Security and Justice Studies and the French Observatory for Drugs and Drug Addiction examined data from Washington and Colorado.

In 2012, these two states became the first to legalise marijuana for recreational use.

The study also assessed cannabis data from Uruguay, which in July became the first country to legalise marijuana use nationwide.

Legalising marijuana increases its use

Results reveal while marijuana use among teenagers in Colorado and Washington remains at the same consistently high levels, its use has increased in those aged over 25.

In Uruguay, 'all indicators of use have risen'.

Such legalisation has led to a significant rise in the number of hospitalisations for patients suffering cannabis poisoning, particularly among tourists, in Colorado and Washington. Cannabis poisoning can cause heart attacks.

Sales of recreational marijuana have also steadily increased in the US, reaching $1 billion in each of the two states every year.

Legalisation has also not eradicated marijuana trafficking in any of the regions where it is permitted.

Yet, legalising cannabis has eased police burdens, as well as reducing the number of court cases.