A new US study has found a significant impact on the price, potency and seizure of illegal drugs in states where recreational cannabis has been legalised.

The study, published in scientific journal Addiction, found that while the price of street cannabis fell, heroin, oxycodone and hydrocodone prices all increased considerably.

The study analysed the staggered implementation of recreational cannabis laws (RCLs) in 11 states compared with those where recreational use remains illegal.

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It used crowdsourced data from Price of Weed and StreetRx regarding the price and quality of illegal drugs which showed street/illegal cannabis prices fell by 9.2% in the states with RCLs, increasing to 19.5% for low-quality product.

Meanwhile, heroin prices increased by 64% and potency by 54%, street/illegal oxycodone prices went up by 7.3% and hydrocodone by 5.1%.

There was a 93% decrease in law enforcement seizures of street/illegal cannabis and a 50%-plus decrease in seizures of heroin, oxycodone, and hydrocodone.

Lead author and assistant professor of population health sciences at Weill Cornell Medicine said: “Our exploratory findings suggest that markets for illegal drugs may not be independent of legal cannabis market regulation.

“As more states move towards legalisation and additional data becomes available, we’ll need to do more research to determine whether recreational cannabis laws cause those changes in the illegal market and what happens in the long-term.”

To access the full report, click here.