My son, age 27, got a prescription for medical marijuana. I'm worried that he smokes way too much. How do I know if he's got a problem or he's just using for reasonable medical purposes. If he does have a problem, what can I do. He's independent, living away from home, financially successful and engaged to be married. By all outward appearances, he seems ok. Bu, he lies to me about when and how much he smokes.