In an observational study on cognitive effects on the use of cannabis in patients that neurocognitive abilities remained stable.
The study that was carried out by researchers from the University of Michigan, Detroit and Windsor in the United States and Canada proved the opposite of the hypothesis that “cognitive functioning would be negatively affected by cannabis poisoning.”
At least 22 medical cannabis patients from Southeast Ontario completed the study. The majority of these were men of an age of 36 years and a level of secondary education.
“The same neurocognitive battery was applied to the patients three times over a period of six hours: at the beginning of the study, after consuming the cannabis product with 20% THC and once more several hours later.”
The result was contrary to expectations and popular opinion.
“Contrary to expectations, performance in neuropsychological tests remained stable or even improved during the acute intoxication stage … and continued to increase during recovery. Interestingly, the rate of failures in performance validity indicators increased during THC. Contrary to our hypothesis, there was no psychometric evidence of a decrease in cognitive ability after THC poisoning. “
Read the full study below: https://www.ncbi.nlm.nih.gov/pubmed/31790276
in Costa Rica. 
