Is Weed Blunting Your Brain? A new study has found that two parts of your brain change in shape and size when you smoke marijuana at least once a week.

Scientists used MRI imaging to monitor the brains of forty 18 to 25-year olds. Half of whom had smoked weed once a week, and half who had never smoked weed or had smoked very little.

They found that the areas of the brain involved in emotion and motivation differed in shape when compared to non-smokers.

“This study raises a strong challenge to the idea that casual marijuana use isn’t associated with bad consequences,” says study leader Hans Breiter.