Hoarders are unable to invite guests to the home or prepare a meal and cannot find their most important possessions because of the clutter.
Hoarding isn't just a problem in the home, it can happen in an office workspace or in cars.
Research from the OCD Foundation reveals that 80 percent of all hoarders have a first-degree relative with the disorder. It can often be triggered by a loss or trauma.
"Sometimes if the parent is a hoarder, it's being modeled directly [by the child,]" said Pike.
Some research has shown an association with the disorder on chromosome 14. "There's a strong genetic link," said Catherine R. Ayers, program director for the Anxiety Disorders Clinic in the VA San Diego Healthcare System.
Researchers like Ayers have found that hoarders have deficits in the executive function area of their brains and have trouble planning, organizing and categorizing.
"Typically, hoarding is resistant to treatment, but we are making headway in intervention," said Ayers, who did a training workshop for clinicians at the conference. "It's a hopeful message."
For most hoarders, cognitive behavior therapy is most effective. In older adults rehabilitation therapy works best. In some studies antidepressant medications are showing promise in conjunction with behavioral and exposure therapy.
"The purpose is for them to learn how to make choices and to tolerate distress in letting go," said Ayers.
Lee Shuer found it agonizing to give up the objects he thought he loved.
In the Smith College study, he had to choose one object to let go. For him it was a "tacky butterfly collar polyester shirt," one he had worn at one of the first shows he played as a musician.
"I thought I could never part with it," he said. "I had to keep track of how I felt about it -- and then come back after a week and talk about it."
At first it was painful to think about giving the shirt to Goodwill, he said. "Then, I started to feel better, and after a couple of days, I was happy I let it go. It totally surprised me and I thought, 'What else can I let go?'"
Today Shuer is director of mutual support services at the mental health agency ServiceNet and runs support groups for hoarders -- "Unburied From Treasures." He continues to serve on a national task force and participates in grant writing for more research.
"All those years, I never imagined not living under this stuff," he said. "Now I can start to see that change is possible."
Now, Shuer confines his collectibles to an 8- by 10-foot room.
"I am enjoying having company over again," he said. "And I actually sold so many of the things I collected that I have the shelf space to display my favorite things."
"In the last six months, it's sparkling -- like a little museum," said Shuer. "I built shelves all around the table where I can do my writing and my art. It's fun, functional and funky. It reflects me and who I want to be."
For more information or help go to the OCD Foundation.