1) how would one know if an elderly relative had clinical depression or was sad because of specific life changes and losses

In a 3 Paper, address the following

1) how would one know if an elderly relative had clinical depression or was sad because of specific life changes and losses?

2) what are the consequences of depression in the elderly ?

3) which behaviors would indicate a person going through depression needs therapy?

4) what kind of therapy would a professional  recommend and why?