WSU researchers see cognitive changes in offspring of heavy cannabis-using rats

I was told a long time ago that when you start smoking pot at a young age, it arrests your mental capabilities at that age. 

Washington State University researchers have seen cognitive changes in the offspring of rats exposed to heavy amounts of cannabis during pregnancy.  The team, led by assistant professor of Integrative Physiology and Neuroscience Ryan McLaughlin, exposed pregnant rats to various concentrations of cannabis vapor and documented how the offspring of those exposed to high amounts had trouble adjusting their strategy to get sugar rewards. The researchers used a new model of exposure, vaporizing cannabis extracts to recreate the way humans most often use the drug.  The pregnant rats received various amounts of vapor. Controls control rats received none, while others were given cannabis-free vapor, or vapor with low or high amounts of cannabis. The vapors, administered in controlled cages over two hour-long sessions per day from before pregnancy through gestation, raised the THC levels in the blood to that of a person who has had a few puffs.

About 60 offspring were submitted to a task designed to test the subject’s ability to adapt to changes in the rules to obtain a reward.  Rats exposed to cannabis in utero appeared to learn the new reward strategy, hitting the correct lever several times in a row, but they would not keep to the strategy long enough to strike the right lever ten times, like the offspring of mothers exposed to less or no cannabis.

McLaughlin notes that the high-exposure rats may not necessarily be less intelligent, just less motivated. They could also be less interested in the task, not want so much sugar, or want to explore other avenues.