Illinois has joined many other states in legalizing medical marijuana. States like Colorado and Washington have legalized recreational marijuana. Advocates pushing for more legalization often say marijuana does not carry long-term negative effects. But a new study from Harvard University and Northwestern University’s Feinberg School of Medicine states that even recreational use of marijuana can have long-term effects on the brain. The study’s senior author Hans Breiter details what he found. Photo: Flickr/Flickr Torben Bjørn Hansen