Nothing wrong with it as long as you don't abuse it.. I know people who hit it hard and it has a profound effect on their life, relationships, work, etc. I also know people who use it and function perfectly normal. With regards to it causing mental issues, the type of people who unfortunately suffer are the type of people who have a high chance of suffering mental issues anyway. If it's not the weed that takes them through the door it could just as easily be some traumatic event in their life, stress or something else.