An 82-year-old male who was recently diagnosed with Alzheimer disease is brought for re-evaluation by his family because of a change in his behavior. He looks sad, is agitated, and states that his life has no meaning and he wishes to die. A complete blood count, ESR, serum electrolytes, folate, B12 levels, thyroid function tests, liver function tests, cerebrospinal fluid analysis, and CT scan of the head are all within normal limits. Psychological evaluation reveals that the patient has mild dementia. What is the best treatment for the patient?