When sober, most rats tended to choose the harder challenge over the easier one, inspired by the prospect of a double dose of sugar. However, when given THC, they stopped bothering with this task, instead choosing the easier but less handsomely rewarded assignment.
“What’s interesting, however, is that their ability to do the difficult challenge was unaffected by THC. The rats could still do the task – they just didn’t want to,” explained study co-author Mason Silveira in a statement.
When the rats were given CBD instead of THC, they carried on choosing the more difficult task over the easy one, an indication that THC, but not CBD, causes the rodents to become lazy. Interestingly, the strength of this effect was directly correlated to the density of a particular cannabinoid receptor in each rat’s medial prefrontal cortex – a brain region associated with effortful decision-making.
Rats that were given a mixture of THC and CBD in equal concentrations also switched to the easier task, suggesting that CBD does not counteract the effects of THC, as is often claimed.
Based on these findings, the study authors suggest that the high correlation between long-term cannabis smoking and poor socio-economic status may be a result of weed-induced laziness rather than any impairments in cognitive ability caused by the drug.