Hoarding disorder

A recognized mental health condition involving persistent difficulty parting with possessions, regardless of their value, to the point that living spaces can no longer be used as intended. It is treatable, and treatment is what makes remediation last.

What kind of thing this is

Hoarding disorder is a recognised health condition in this field. This definition comes from a primary government source. Where the wording matters we quote the standard rather than paraphrase it, because paraphrase is where precision leaks out.

Where you will meet it

This is a clinical term, and using it rather than a description of the mess is the difference between a referral that goes somewhere and one that does not.

Why the wording matters

This site defines terms in under forty words wherever it can, and attaches the practical consequence rather than leaving it implied. A definition that tells you what something is, without telling you what follows from it, is trivia at a moment when nobody has room for trivia.