The effects on intelligence are also pretty well-studied. Chronic use of Marijuana does make you dumber, and you are also less intelligent when high if you are an occasional user.

Studies suggest this isn't permanent for users over 25 (or at least there's not enough data to say that), but it apparently takes years for the effect to wear off after chronic use and it might be permanent if you are a young user.

This is not to say that I am against consenting adults using Marijuana, but the idea that there are no effects other than making you happy is ludicrous.