Marijuana affects brain functioning during visual stimuli

An Indian origin scientist and his team have found that different ingredients in marijuana appear to affect regions of the brain differently during brain processing functions involving responses to certain visual stimuli and tasks.

Sagnik Bhattacharyya, MBBS, MD, PhD, at the Institute of Psychiatry, King’s College in London, and colleagues studied 15 healthy men, who were occasional marijuana users, to examine the effects of 9-tetrahydrocannabinol (9-THC) and cannabidiol (CBD) on regional brain function during salience processing, which is how people perceive things around them.

The authors used functional MRI images to study each participant on three occasions after administration of 9-THC, CBD or placebo. Study participants performed a visual oddball task of pressing buttons according to the direction arrows on a screen were pointing, as a measure of salience processing.

“Pairwise comparisons revealed that 9-THC significantly increased the severity of psychotic symptoms compared with placebo and CBD whereas there was no significant difference between the CBD and placebo conditions,” the researchers said.

9-THC had a greater effect than placebo on reaction time to non-salient relative to salient stimuli.

This was associated with modulation of both prefrontal and striatal function by 9-THC, augmenting (increasing) activation in the former region and attenuating (weakening) it in the latter.

“Moreover, in the present study, the magnitude of 9-THC’s effect on response times to non-salient stimuli was correlated with its effect on activation in the right caudate, the region where the physiological effect of 9-THC was linked to its induction of psychotic symptoms,” they wrote.

They concluded that “collectively, these observations suggest that 9-THC may increase the aberrant attribution of salience and induce psychotic symptoms through its effects on the striatum and lateral prefrontal cortex.”

When the effects of CBD were contrasted with 9-THC and placebo with respect to the visual task there was a “significant effect” in the left caudate with CBD augmenting (increasing) the response and 9-THC attenuating (weakening) it.

“These effects suggest that CBD may also influence the effect of cannabis use on salience processing – and hence psychotic symptoms – by having an opposite effect, enhancing the appropriate response to salient stimuli,” the researchers added.

The findings appeared in the January issue of Archives of General Psychiatry, one of the JAMA/Archives journals.

Marijuana can affect your Sex drive!

A new study from La Trobe University in Melbourne has found that men who regularly smoke pot are four times more likely to have trouble reaching orgasm. During the study, lead researcher Marian Pitts analysed the data collected as part of a 2005 telephone survey of 16- to 64-year-olds.

It showed that overall, 8.7 per cent of respondents said they had gotten high in the last year, with twice as many men (11.2 per cent) admitting to marijuana use as women (6.1 per cent). Although male smokers experienced sexual problems, they still had more partners than non-smokers, reports New Scientist.

The findings showed that marijuana users were twice as likely to have had two or more sex partners in the previous year than men who didn't smoke pot. Pitts' team found an even stronger trend for increased sexual activity among female smokers, who were also seven times more likely to have been diagnosed with a sexually transmitted infection in the last year than non-smokers. However, they had no more problems in the bedroom than abstainers. The new study supports the results of the research led by Marie Eloi-Stiven at Weill Medical College of Cornell University in New York, which found that marijuana users were far more likely than others to take Viagra.