Do you have a hard time letting go of your possessions when they’re of no use to you anymore? When does simple nostalgia turn into something more serious? Earlier this month, a decomposed body was found by forensic cleaners in Sydney apartment, and police think it’s possible that the mummified man may have died a whole decade ago. It is now thought that the apartments owner suffered from hoarding disorder.

Hoarding disorders impact at least 1.2 million Australians. We chatted to Dr Melissa Norberg from Macquarie University’s Department of Psychology to find out what can cause them, and how they can manifest.