The myth that smoking marijuana with tobacco will make users more stoned has been debunked by scientists.
Cannabis users across the world have long believed that sprinkling a handful of tobacco in with the herb improves the high.
But in the first study of its kind, researchers delving into how both substances interacted when inhaled together found no such effects.
However, they did note that mixing the two together may help to lessen the memory impairment caused by smoking cannabis.
The new University College research suggested this could be because nicotine has previously been proven to sharpen the mind.
As legalisation of cannabis becomes prevalent, researchers said it is essential that any changes in its policy consider the interrelationship between tobacco and marijuana.
Researchers also found that smoking cannabis and tobacco together can temporarily increase blood pressure and heart rate.
Experts said the findings are worrying, considering the long-term health dangers that are already known about smoking tobacco-related products, including heart disease and various forms of cancer.
Lead author Chandni Hindocha, of the university's clinical psychopharmacology department, said: 'There's a persistent myth that adding tobacco to cannabis will make you more stoned, but we found that actually, it does nothing to improve the subjective experience.
'Surprisingly little research has been done on how tobacco might alter the effects of cannabis.
'As cannabis gets legalised in more countries, it is essential that any changes in cannabis policy consider their interrelationship.'
Professor Val Curran, who was also involved in the research, added: 'There is a clear public health implication here, suggesting that smoking tobacco with cannabis does not improve the stoned feeling but is still worse for physical health.'