We are all pack rats to some degree. We hoard, collect and buy more stuff than we have room to store.
But what if something in our brains made us incapable of throwing things out? Janie Allocca and Lorraine Brennan both live with a psychological disorder called compulsive hoarding -- an urge to hold on to even the most mundane objects, even when they take over their lives.
In a 2007 interview with ABC News, Brennan said that she had been hoarding for nearly 20 years. She lived in a two-story house in Massachusetts with her father, son and fiancé. Most rooms in the house were cluttered, and some were even unusable. The bedroom-office that she shared with her fiancé was overrun with stuff they'd tried unsuccessfully to get rid of at a yard sale. Lorraine's purse was bursting with junk mail and receipts.
Brennan's hoarding was not only ruining her life but affecting her entire family. Her son couldn't bring friends home from school. Brennan and her fiancé had been engaged for eight years, but he couldn't commit to marrying her because of the clutter.
Many hoarders are also compulsive shoppers. Allocca had accumulated so much stuff that she used her own house as a storage facility and lived with her mother.
"I remember collecting, and keeping, and hoarding things since I can remember," Allocca told ABC News in 2007. "And now I am just living around the piles and piles I need to get rid of."
"I have so much stuff that my house is totally unlivable," she continued. "There's no place to sit down. I can't get to the kitchen. I can't have anyone over for tea even though I have everything for tea. My collecting is taking up the space where I normally would live."
There's a fine line between simple clutter and extreme hoarding. Most hoarders, observers say, are physically incapable of throwing things out. They can't live in, or use, rooms like the kitchen for their intended use. They also experience extreme distress over their condition.
Hoarding is considered a subset of obsessive-compulsive disorder, but that may soon change. New research is finding that hoarding may be a special disorder completely separate from OCD.
Dr. David Tolin, director of the Anxiety Disorders Center at the Institute of Living in Hartford, Conn., has devoted his career to studying what goes on inside the mind of a hoarder.
"At the moment, compulsive hoarding hasn't been fully defined by the psychiatric and psychological communities," he said. "One of the things that we wanted to do was to understand some of the brain mechanisms behind compulsive hoarding."
Allocca was part of a study Tolin conducted to see which parts of a hoarder's brain become active when they are faced with making decisions. She was hooked up to a brain-scan machine and asked to look at pieces of her mail and decide whether she wants them to be thrown out. She then had to watch the mail get shredded.