Scientists warn, the fact that anxiety drugs use the same addictive reward pathways in the brain as heroin and cannabis, means they can be just as addictive as the drugs.

The researchers from Switzerland and USA found benzodiazepine drugs like Valium and Xanax have a calming effect by pushing a neuro-transmitter into action, in turn activating dopamine, the gratification hormone in the brain, the same reward pathway some illegal drugs like heroin activate.

Writing in the journal Nature, they are hopeful these findings may help in the development of next generation non-addictive benzodiazepines.

Prescribed by NHS, Roche’s Valium, generic name diazepam is the best known and most popular of the benzodiazepine class of drugs, and along with Ativan, it was amongst a host of other prescription drugs found in Michael Jackson’s blood when he died last year.

Benzodiazepines, the study found worked by binding to a particular part of the neuro-transmitter called gamma-aminobutyric acid, which finding may help in the development of similar benzodiazepines, which binding to a different part could offer similar benefits, but without the addictive side effects.