I will give you some ideas if you are stuck,
I was in the same position in GCSE film studies and I'm not doing media and hoping to do Film studies at uni.
So if the depression thing you were thinking about the first thing that came to mind would be a first person narrative of the struggle with a mental illness.
You should have a character in which has a mental illness and does something terrible which lands then in a hospital where they go through the worst treatment (make it set when electro shock therapy was allowed) and he eventually commits suicide becuase of his terrible treatment becuase they were only making him worse.