Researchers recently studied the effects of various antidepressant drugs on 2235 older patients for 8-12 weeks. They found, that although the drugs worked better than placebo, response rates were not much better than placebo unless the patient was depressed for more than 10 years!
I think that one reason the medications did not work very well is that every patient is different when it comes to response to therapy. Many patients are under dosed or require multiple medication. (Many of my high blood pressure and diabetic patients are on multiple medications, so why not mental health disorders?) Some patients may not see an adequate response for more than 12 weeks.
The authors of the study suggest substituting or adding psychotherapy, which I think is a great idea. Unfortunately counseling is very expensive and time consuming and MOST insurance plans will NOT pay enough for short term or long term therapy. The best therapist DO NOT accept insurance anyway and weekly costs can range from $100-$150/week.
Because of the social stigma of mental health and since most Seniors (and working people) cannot afford this, they usually refuse this option.