Cannabis on the brain
19 Jan 2012 by Evoluted New Media
For the first time, scientists have gained experimental evidence of the effects of specific chemicals found in cannabis on the brain.
Scientists from the Institute of Psychiatry at King’s College London studied the effects of two main components of cannabis – ?9-tetrahydrocannabinol (THC) and cannabidiol (CBD) – in 15 healthy men who were occasional cannabis users.
They used functional magnetic resonance imaging to study each participant on three occasions after administration of THC, CBD or a placebo. The men then performed a visual oddball detection task so the researchers could understand the importance each individual attached to a specific stimulus.
THC was shown to weaken the activation of the striatum and increase activation of the lateral prefrontal cortex. This was because the THC increased the individual’s response to normally insignificant stimuli, and decreased the response to significant stimuli.
The researchers say this helps to explain why smoking cannabis can make people feel paranoid – or in the most extreme cases, experience psychotic episodes. Individuals attach special importance or meaning to normally insignificant experiences or stimuli.
“Our findings help shed further light on the mental and public health consequences of cannabis,” said Dr Sagnik Bhattacharyya, who led the research with Professor Philip McGuire.
“The increasing prevalence in Europe and the UK of more potent forms of cannabis with high levels of THC is worrying as there is a strong evidence of a link between THC and psychosis in some individuals.”
CBD was shown to have the opposite effect on the brain, and increased the response of the left caudate – the area of the brain weakened by THC. Researchers believe CBD could prove useful in treatments for psychiatric conditions, although more research is necessary.
The research – supported by a Joint Medical Research Council/Priory Clinical research training fellowship and a grant from the Psychiatry Research Trust – was published in Archives of General Psychiatry.
