Unfortunately, destructive clutter can be a symptom of bipolar disorder or depression. People who are depressed can lose their drive to do most everything, and that may include cleaning up their living spaces and keeping things in order.
Over at the blog Psychology of Clutter, Dr. Ragan writes:
When people do not feel emotionally strong they will often let their environments fall into disarray. If you start therapy and/or start medication, you can begin to feel better, only to be hindered by what is going on outside of you. I often use the term “depressed lifestyle” with my clients. It is hard to feel good when your house or apartment looks like a bomb went off, your friends don’t call anymore, you’ve gotten fat and you look like hell.
If you have a friend or relative who is living in an extremely cluttered living space, you should encourage him or her to seek help from a professional. Sometimes the most meticulously neat person can find themselves in a downward spiral that results in a depressive state surrounded by clutter and disarray. This 180 degree turn for the worse can be a telltale sign that the individual is in need of help.