Researchers at Maastricht University and IZA Bonn have carried out a statistical study of 54,000 course grades by students and have concluded that those students who were unable to purchase cannabis were likely to get 5% better grades.
This may be true, or it may not. The assumptions made are, to say the least, unscientific.
1. The assumption is that because cannabis availability was restricted in 2011 the resulting 5% improvement in grades by some students is directly related to that, whereas it could be due to many other factors including different grading criteria or, dare one suggest it, better teaching methods.
2. No attempt has been made to assess the relationship between occasional and heavy consumption.
3. The report is a "statistical analysis" and not a medical or physiological study. The phrase "lies, damn lies and statistics" comes to mind.
4. As ever, the most useful information is contained in the small print: the researchers state that the claimed 5% fall in grade attainment is equivalent to that observed in the US when students reach the age for legally consuming alcohol. Worst case conclusion: excessive consumption of cannabis is broadly as harmful as excessive consumption of alcohol. Shock-horror!