Define "over medicating". Personally, I think it's a more of an opinion then anything.
Many diseases/illnesses need medication - often more then one medication as well (cancer, seizure disorders, endocrine disorders, respiratory diseases, etc).
If you are talking only about pain management and pshychiatric problems, I think it depends on the degree of the illness. Should someone in end stage cancer be limited to pain medications? I don't believe so. I think it's cruel to have someone in chronic pain solely because the medications have the potential for abuse. Do I think someone who had a back strain two years ago, fails a tox screen for multiple illegal or other non perscribed drugs, and refuses any other treatment other then narcotics (such as pshyscial therapy, etc) should be given fentanyl patches for the rest of their life? No.
And I think pshychiatric illness are under treated in many ways. There is a very clear difference in between a schizophrenic who is medicated and one that is either not medicated, or not medicated enough. There are some patients who are on a grocery list of medications- and are violent/destructive when I pick them up when they haven't been compliant with their meds- but when I see then on their medications they are a normal functioning person.