Ask for a refund, depression sucks, I've been dealing with mental illness. It sucks but it does not give someone an excuse not to refund if the commissioner requests.
If they've done some of it (like a sketch) you can ask for a partial and take that with your sketch. If it's been a few months and you've seen nothing you are in all right to get a refund. People should not use mental illness for a reason to not do work owed and should be offering refunds.