Does smoking marijuana have negative effects on your health?

I just got into an argument with a habitual pot smoker. His claim is that smoking pot helps him in life, and the media portrays it as bad is propaganda. I cited my experience with pot heads, and they were some of the moodiest, bitter, lazy, all talk no action freeloaders I have ever met. Of course people who smoke are going to justify the use, but what are the true, prolonged effects? Sure it might be natural, but so is tobacco.