These are pages with a very good description of causes and symptoms of hoarding: About Hoarding. Hoarding Disorder.
A simple guide to helping a hoarder yourself – Health Navigator New Zealand – How To Help A Hoarder
Support Groups and Professional Services
Psychology Today NZ – Hoarding Disorder to find therapists who can help with hoarding behaviours, click the Find Counselling drop down arrow in the blue banner at the top and enter your city. Click GO. Click the Issues button. Click Show More Issues. Click Hoarding.
The Taranaki DHB have written an interesting document a few years ago: Hoarding And Squalor Guidelines
The Southern DHB wrote something very similar: Good Living Conditions Southern
Community & Public Health Canterbury Enabling Spaces – Supporting older people who hoard in Canterbury
This UK public Facebook group shares useful information and articles for people with hoarding behaviours, professionals who help them and family and friends. https://www.facebook.com/HoardingDisordersUK/