For the first time, scientists have proven that cannabis harms the brain. But the same study challenges previously-held assumptions about use of the drug, showing that some brain irregularities predate drug use.

Professor Dan Lubman, from Turning Point Alcohol and Drug Centre and Monash University, along with a team of researchers from Melbourne University have conducted a world-first study examining whether these brain abnormalities represent markers of vulnerability to cannabis use.

“Previous evidence has shown that long-term heavy cannabis use is associated with alterations in regional brain volumes,” Professor Lubman said.

“Although these changes are frequently attributed to the neurotoxic effects of cannabis, no studies have examined whether structural brain abnormalities are present before the onset of cannabis use until now.”

To fill this void in present studies, Professor Lubman and his team recruited participants from primary schools in Melbourne, Australia, as part of a larger study examining adolescent emotional development.

Of the 155 original participants who underwent structural magnetic resonance imaging at age 12, 121 completed a follow-up survey measuring substance use four years later. It was found that by age 16, 28 participants had commenced using cannabis.

“This is an important developmental period to examine, because although not all individuals who initiate cannabis use during this time will go on to use heavily, early cannabis use has been associated with a range of negative outcomes later in life,” Professor Lubman said. [continue reading…]