New research helps to explain how marijuana works in the brain, with study participants responding differently to THC and CBD.
Marijuana can have very different effects on people's behavior, producing a mellow calm in some and anxiety or even paranoia in others. Researchers have not been clear on why this variation exists, but a new study suggests that the different -- virtually opposing -- actions of the two key chemicals in marijuana, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), may be the answer.
Researchers had 15 men who had only smoked pot a few times in their lives take pills that contained THC, CBD, or a placebo (a flour-filled capsule). Then they had the participants complete a computer task that measured their reaction times to typical vs. "oddball" stimuli. Most people react more strongly to unexpected stimuli, so the men's reaction times would give researchers a clue into how their responses to environmental triggers may shift when they are exposed to the different compounds.
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The men underwent brain scans while they carried out the computer test, so that the team could see which areas of the brain were more active under the different treatments. They also filled out questionnaires about their subjective experiences, including whether they experienced delusional thoughts or hallucinations.