lying bipolar disorder

Is Bipolar disorder a highly used scapegoat?
Basically a doctor can diagnose you with Bipolar disorder strictly based on what you tell him, correct?
If that is the case, many people can lie to the doctor and use their diagnosis as an excuse for poor behavior!
I remember a few years ago when Bobby Brown was asked about his marijuana usage and he said he needs it because he is bipolar. Do they really prescribe marijuana for this condition?
People can, and do, lie to get medications. However, someone who is truly bipolar will still need the help. We all know Bobby Brown lied, and psychiatrists have a wide variety of medications that don’t include marijuana which they can try. Pot has a tendency to create paranoia and anxiety in some people, so I doubt it’s part of the treatment for people who are bipolar. It’s used more for cancer and glaucoma patients, if it’s used at all.