This is a page with a very good description of causes and symptoms of hoarding: About Hoarding
Support Groups and Professional Services
Psychology Today NZ – Hoarding Disorder Enter your postcode in the box on the right to find therapists who can help with hoarding behaviours.
Auckland Libraries has several books on the subject of understanding and managing hoarding behaviours:
The Taranaki DHB have written an interesting document a few years ago:
The Southern DHB wrote something very similar:
This UK public Facebook group shares useful information and articles for people with hoarding behaviours, professionals who help them and family and friends.