Crime in Denver, the capital of Colorado, has dropped by 10 per cent since last year - reassuring those who feared it would rise after the first legal marijuana stores opened in the state on 1 January.

The statistics published by Denver authorities show that crime overall dropped by 10.6 per cent, while violent crimes including sexual assault and homicide fell by about 5 per cent in total. Meanwhile, property crime such as motor theft fell by around 11 per cent in the city as a whole.

While the fall has not been directly linked to the legalisation of marijuana, the trend is likely to bolster pro-cannabis campaigners and those who welcome the $1.9million (£1.2 million) in tax the government has so far gathered from legal cannabis sales.

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When medical marijuana stores are included, the Colorado collected $3.5 million (£2.1 million) in taxes since it became the first US state to legalise cannabis in 2012, with commercial sales beginning at the start of the year.

Shape Created with Sketch. Cannabis around the world Show all 13 left Created with Sketch. right Created with Sketch. Shape Created with Sketch. Cannabis around the world 1/13 Morocco Farmers destroy cannabis plantations under Moroccan police supervision in the northern Moroccan Larache region, pictured here in 2006 AFP/Getty images 2/13 Colorado Growing business: Cannabis on sale at River Rock Wellness Sam Adams 3/13 Oakland Oaksterdam in Oakland, California, is the world's only university dedicated to the study and cultivation of cannabis Alain Jocard/AFP/Getty Images 4/13 Seattle A cannabis smoker marks the start of the new law by the Space Needle in Seattle Getty Images 5/13 China Cannabis growing wild in China, where it has been used to treat conditions such as gout and malaria 6/13 Uruguay Uruguay has voted to make the country the first to legalize marijuana AFP/Getty 7/13 Colorado A groundswell of support from the public led to full legalisation in Colorado Getty Images 8/13 Berlin A man smokes licenced medicinal marijuana prior to participating in the annual Hemp Parade, or 'Hanfparade', in support of the legalization of marijuana in Germany on August 7, 2010 in Berlin, Germany. The consumption of cannabis in Germany is legal, though all other aspects, including growing, importing or selling it, are not. However, since the introduction of a new law in 2009, the sale and possession of marijuana for licenced medicinal use is legal. Sean Gallup/Getty Images 9/13 UK The UK latest figures show 2.3 million people used cannabis in the last year AP 10/13 Amsterdam Tourists visiting Amsterdam will not be banned from using the city’s famous cannabis cafes Getty Images 11/13 Merseyside These 25 cannabis plants, seized in Merseyside police, could have generated a turnover of £40,000 a year 12/13 San Francisco April 20, 2012: People smoke marijuana joints at 4:20 p.m. as thousands of marijuana advocates gathered at Golden Gate Park in San Francisco, California. The event was held on April 20, a date corresponding with a numerical 4/20 code widely known within the cannabis subculture as a symbol for all things marijuana. Reuters 13/13 Spain A cannabis users' association will pay the town of Rasquera more than €600,000 a year for the lease of the land 1/13 Morocco Farmers destroy cannabis plantations under Moroccan police supervision in the northern Moroccan Larache region, pictured here in 2006 AFP/Getty images 2/13 Colorado Growing business: Cannabis on sale at River Rock Wellness Sam Adams 3/13 Oakland Oaksterdam in Oakland, California, is the world's only university dedicated to the study and cultivation of cannabis Alain Jocard/AFP/Getty Images 4/13 Seattle A cannabis smoker marks the start of the new law by the Space Needle in Seattle Getty Images 5/13 China Cannabis growing wild in China, where it has been used to treat conditions such as gout and malaria 6/13 Uruguay Uruguay has voted to make the country the first to legalize marijuana AFP/Getty 7/13 Colorado A groundswell of support from the public led to full legalisation in Colorado Getty Images 8/13 Berlin A man smokes licenced medicinal marijuana prior to participating in the annual Hemp Parade, or 'Hanfparade', in support of the legalization of marijuana in Germany on August 7, 2010 in Berlin, Germany. The consumption of cannabis in Germany is legal, though all other aspects, including growing, importing or selling it, are not. However, since the introduction of a new law in 2009, the sale and possession of marijuana for licenced medicinal use is legal. Sean Gallup/Getty Images 9/13 UK The UK latest figures show 2.3 million people used cannabis in the last year AP 10/13 Amsterdam Tourists visiting Amsterdam will not be banned from using the city’s famous cannabis cafes Getty Images 11/13 Merseyside These 25 cannabis plants, seized in Merseyside police, could have generated a turnover of £40,000 a year 12/13 San Francisco April 20, 2012: People smoke marijuana joints at 4:20 p.m. as thousands of marijuana advocates gathered at Golden Gate Park in San Francisco, California. The event was held on April 20, a date corresponding with a numerical 4/20 code widely known within the cannabis subculture as a symbol for all things marijuana. Reuters 13/13 Spain A cannabis users' association will pay the town of Rasquera more than €600,000 a year for the lease of the land

“All the naysayers who were against marijuana legalization are eating crow about now. Colorado’s weed sales just keep trending up, and with the sales of legal weed, they are improving their schools and reducing overall crime rates,” yoga teacher Christina Sarich wrote about the drop in crime in an article that has gone viral on pro-cannabis websites.

However, the latest figures coincide with the publication of a study by scientists from the University of Pennsylvania, who claim that marijuana can cause sleeping problems.

People who had taken the drug before they were 15 were twice as likely to suffer these complications, results showed.