Im 21 and I tell the doctor the truth if he seems like an understanding doctor. I have gotten a lecture from a doctor because I said I smoke a pack a day. I know it's unhealthy so leave me the fuck alone. So now if it looks like I'm going to get a lecture about cigs and weed I just say no to all their questions. If the doctor doesn't look like an ass who is going to tell me about how evil my life is than I go ahead and tell him the truth.