An eye-opening new studying indicates that toking up might not always be a good idea.

The study, published by researchers at the Institute of Psychiatry at King’s College London, found that high-strength cannabis can damage nerve fibers that handle the flow of messages in the brain, based on scans of people who regularly smoked strong marijuana, according to a Guardian report.

They noticed that there were differences in the white matter that connects the two hemispheres of the brain and carry signals between the two, something not seen in those who did not smoke cannabis or smoked only lesser forms of marijuana.

The scientists think that THC, the active ingredient in cannabis, is responsible for this change. Most forms of cannabis have about 2 to 4 percent THC, but more potent varieties can contain up to 14 percent.

The researchers came to their conslusions with two scanning techniques: magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI). They looked at the brains of 56 patients who had reported an episode of psychosis as well as 43 healthy volunteers.

The results were interesting: they found about a 2 percent greater “mean diffusivity” in the corpus callosum of those who used high-potency cannabis, which indicates that the white matter in the brain is less efficient.

There is a possibility that those with damaged white matter are more likely to smoke skunkier weed to begin with, but the correlation is a strong indication that there may be a connection.

As a result, people may need to be careful on how they use cannabis, and be aware that there may be a big difference in smoking low and high potency marijuana, and that perhaps not all types of marijuana are created equal when it comes to safety.