Cannabis smokers warned they risk poorer exam grades

Dutch study finds mathematics results suffer most from dope consumption - findings sure to fuel debate over steps towards legalisation

If you want to do well in your exams, especially maths, don't smoke dope.

This is the finding of a unique study that is likely to be fiercely debated by those in favour of and those against the liberalisation of cannabis laws. Economists Olivier Marie of Maastricht University and Ulf Zilitz of IZA Bonn examined what happened in Maastricht in 2011 when the Dutch city allowed only Dutch, German and Belgian passport-holders access to the 13 coffee shops where cannabis was sold. The temporary restrictions were introduced because of fears that nationals from other countries, chiefly France and Luxembourg, were visiting the city simply to smoke drugs, which would tarnish its genteel image.