This question was posted quite a while ago, som hopefully you have received your answers elsewhere. I am not aware of a single tool that covers all aspects of mental health in community-dwelling elderly. You also need to decide if the tool should be used for screening purposes or for more specific samples of the elderly population. In addition you will need to consider who is the respondent; the patient, his/her relatives or health care professionals? In order to cover the most prevalent conditions, which should be depression, anxiety (or those combined) and dementia/cognitive decline I think you will need separate tools for all conditions that you will cover. Alternatively you could use the Hospital Anxiety and Depression Scale to evaluate these conditions combined.