Cannabis users who start by smoking skunk up to five times as likely to become dependent, study suggests

There is growing momentum behind national and state legalisation but little regulation or research of cannabis potency despite increasing availability of high THC strains

High-potency strains have come to dominate markets in UK and US over past two decades (Getty)

Cannabis users whose first experience with the drug is with potent “skunk” strains are nearly five times more likely to go on to show signs of dependence, US researchers have said.

Researchers found higher concentration of THC, the molecule which causes its psychoactive “high”, increased the likelihood that users would develop cravings or risky drug use that disrupts their day-to-day life.

Despite medical or recreational cannabis use being legalised in a growing number of states and countries there is little regulation on potency - even though this is routine for drugs like alcohol which also cause impairment and dependence.

“THC has linearly increased over two decades,” said Dr Brooke Arterberry, an assistant professor of psychology at Iowa State University who led this research.

“Based on the results, states may want to think about the available potency levels of cannabis products, especially with the changing legal landscape of cannabis.”

Increases in THC content have been made possible because of modern growing techniques and in America average levels have risen from 3.5 per cent THC in 1994 to 12.3 per cent in 2012.

In the UK high-potency skunk has pushed out virtually all other types, and experts warn that mental health disorders like psychosis are more common in people who use these stronger strains.

For the study, published in the journal Drug and Alcohol Dependence, Dr Arterberry and colleagues used data from a long-running health survey of young people age 11 to 26 who have family history of substance abuse.

In annual follow-ups, users who reported that they had started smoking skunk – with an average THC content of 12.3 per cent – were 4.8 times more likely to have one or more symptoms of cannabis use disorder when compared to those smoking a 4.9 per cent strain.

Cannabis is not typically thought of as addictive in the same way as heroin, cocaine, or even alcohol, where withdrawal can have serious physical health effects. However it can cause irritability, sleep disruption and other effects that make heavy users dependent.

“This is the first step toward understanding the influence of potency,” Dr Arterberry said. “While more research is needed, the risk associated with higher potency highlights the need for early intervention and targeted prevention efforts.”