Clinical hoarding affects up to 6 percent of the world population, twice as many as OCD, yet it is a largely misunderstood disorder.
In the US 10 percent of households rent an extra storage space away from where they live, to contain stuff they don't really need
And those numbers are set to increase with the world's population ageing.
Professor Randy Frost may know more about the disorder of hoarding than anyone on earth.
Frost is psychology professor at Smith College in New England. He is the author of numerous books on the subject including Buried in Treasures: Help for Compulsive Acquiring, Saving and Hoarding.
Hoarding becomes a disorder, he says, when there’s a persistent “difficulty discarding or parting with possessions regardless of their actual value.”
Many of us are reluctant to part with possessions, however hoarding becomes problematic when moving around and functioning at home is hampered by clutter, Frost says.
“If you can't cook in your kitchen because of the clutter, we can't sit down and eat at the table or you can't sit on your couch.
“Clutter really is a defining feature of how serious a problem is, but that clutter is a result of this difficulty discarding. We think it's somewhere between 2 percent and 5 percent of the population.”
Our understanding of the psychological underpinnings of hoarding are improving, he says.
“Before we understood hoarding disorder it was thought that this disorder involved people saving things that were worthless and worn out.
“It's more than that, they do save things that most people would consider worthless and whatnot, but in truth, people with this problem save everything.
“Even though these things seem precious, very little time is spent interacting with them.”
Motivations for hoarding may include a desire for safety and comfort and an aversion to wasting things, he says.
“One of my early clients at one point told me when I showed up at her home, she said 'I had such a terrible week. I just wanted to gather all my treasures around me'.
“For many people with hoarding disorder, there is a sense of responsibility, responsibility for making sure the possession is not wasted. Instead of throwing it into the landfill, I save it because I don't want to waste it, in a sense a form of environmentalism.”
Although there may be signs in early life, the problem tends to worsen as we age, he says.
“The real dysfunctional aspects of hoarding don't show up until a little bit later, the 30s and 40s and recognition by the person that there's a problem often doesn't show up till a decade or so after that.”
Hoarding behaviour can fracture families, Frost says.
“We see people with hoarding disorder are more likely to have experienced a divorce or separation from a life partner, largely because of the hoarding problem. If the hoarding starts early, they’re less likely to ever get married.”
Frost has encountered some extreme examples of hoarding disorder over the years.
“[In] one ne of the most extreme cases I had was a home that was condemned, and they brought in a cleaning crew to clean it out.
“And what had happened is that it had gotten very unsanitary. So there was rodent infestation, cockroach infestation, they had animals in the apartment so it was filled up four or five feet high without any real pathways through. The fellow with a hoarding problem, his sister lived there, and she was blocked in, the social worker tried to reach her and there was a wall of stuff between them and she couldn't reach this elderly woman.
“So that was one of the more severe cases that could have turned deadly.”
People with this condition experience an intense shame, he says.
“It is very stigmatising, you can see why people with hoarding disorder frequently hide it from other people - the doorbell rings and they don't they don't answer it. Many children who grew up in hoarded homes describe this as ‘doorbell dread’.
“If someone rings the doorbell unexpectedly, everyone's scurrying around trying to figure out how we're going to hide.”
One form of therapy Frost has had success with is helping hoarders process the objects they are bringing into the house.
“We did a study recently where we went into people's homes, people with hoarding problems, and we had them pick out things that were difficult to let go of. And we asked them to simply describe those things to us to tell us about them. And at the end of about a four or five-minute description, they were more likely to let it go.”