Forbes.com 28 November 2015
There’s been a long and heated debate about whether marijuana actually triggers long-term changes in a person, both neurologically and psychologically. Some research has found that pot is linked to psychotic symptoms, and it’s certainly been linked to schizophrenia across multiple studies. However, it’s a bit of a chicken-or-egg problem, since it can be difficult to tell which is the pre-existing “condition,” the pot smoking or the psychological/psychotic symptoms. Now, a new study from King’s College London finds that smoking skunk, a high-potency variety of pot, is linked to changes in the white matter connections between the two hemispheres of the brain. And this seems to be true whether a smoker experiences psychosis or not.
Skunk has higher levels of the psychoactive compound Δ9-tetrahydrocannabinol (THC) than “regular” pot, and has become much more prevalent in recent years, as people seek out more potent versions of the drug.
The researchers scanned the brains of 56 people who had sought treatment for a first episode of psychosis, and 43 healthy controls. The team looked at the density in the brain’s corpus callosum, the vast network of white matter tracks that extend from neurons in one hemisphere to cells in the other. Damage to the white matter connections means less efficient communication between brain cells, which itself can be linked to cognitive problems.
It turned out that there some significant links between how often a person smoked and how likely they were to have changes in their white matter: People who smoked skunk more often had a greater likelihood of damage their white matter than people who smoked less frequently or who smoked lower-potency version. And using skunk was linked to white matter damage regardless of whether or not psychotic symptoms were reported.
“We found that frequent use of high potency cannabis significantly affects the structure of white matter fibres in the brain, whether you have psychosis or not,” said author Paola Dazzan. “This reflects a sliding scale where the more cannabis you smoke and the higher the potency, the worse the damage will be.”