I had a one-time but total psychotic break from smoking weed, it was not fun and took a very long time to recover from. I had been a daily user for years, quit for about a month, and then smoked a small amount I had left over. I hadnt had an adverse reaction like that before or since. I became a daily user again for maybe 6-8 months, but I've since quit.

I'm not saying it will happen to you, and I'm not trying to preach about the dangers, but this was my experience, and it was very bad. I would not agree with someone trying to sell a line of "reefer madness" as it helped me through some pretty rough times. But when it didn't, I had some negative side effects too. I def don't think there is zero negative effects to using it.