It's good that you are so conserned, but the reality is that just because a person is messy and lives in filth, doesn't mean that they suffer from any form of mental illness, including depression or anxiety.
I have a coulple friends that are absolute slobs, but they are very well adjusted, successful, and mentaly healthy people.
For example: I suffer from off the chart Severe Depression, and yet my home and car are absolutly spotless. Almost to the point of perfection.