Employment Law Questions? Ask an Employment Lawyer.
Your employer may wish to discuss with you your plans to return and the basis for your request. They may require more information. They may also want to know if you want your paid vacation given to you while you are gone. These are all legitimate reasons for asking to speak with you, so I would not assume the worst based on their desire to talk with you.
If your PCP agrees that you should be out of work, then yes it is not unreasonable or even uncommon to be off of work for 4 weeks to depression. I have seen periods longer than that.