(CBS News) What makes hoarders feel the compulsive need to hang onto everything?
About 5 percent of the world's population are clinical hoarders, according to the International OCD Foundation, saving objects ranging from food wrappers, old newspapers to animals because they simply can't let go of them.
New research examines the brains of people with compulsive hoarding to find out what leads them to this behavior which can often lead to unsanitary and dangerous living conditions.
In a new study published in the August 6 issue of the Archives of General Psychiatry, researchers at the Institute of Living at Hartford Hospital in Conn., used fMRI machines to measure the brain activity of people when they made decisions about whether to keep or throw away a possession.
The researchers compared the scans of 43 people diagnosed with hoarding disorder, 31 people with obsessive-compulsive disorder (OCD) and 33 healthy individuals. According to the Mayo Clinic, hoarding may be a symptom of OCD but many people who hoard don't have other OCD-like symptoms.
Compared with healthy people and those with OCD, the researchers found distinct patterns of abnormal activity in the anterior cingulated cortex (ACC) and insula in the brains of people who had a hoarding disorder. Those areas of the brain are tied to decision-making processes. When the researchers presented subjects with an object that did not belong to them, the hoarders showed lower activity in those brain regions than their counterparts' brains revealed on the fMRI scans.
However, when they were presented with an object that they owned, the hoarders' brains showed "excessive" signals on the scan, unlike the other two groups. The other subjects' brains showed no such activity when confronted with a decision to throw out a personal item. The researchers say their findings emphasize the problems in the decision-making process that contribute to hoarders' inability to throw items away.
"That brain network goes into hyperdrive, starts freaking out," study author Dr. David Tolin, a psychologist at the Institute of Living in Hartford, Conn., told WebMD. "The task seems to overload the network."
As such, the study showed that the group of subjects with hoarding disorders discarded significantly fewer items that belonged to them than subjects in the other two groups. The authors say the links between excessive functions of these brain regions in people with hoarding disorder should be researched further.
"This illumination is important because although it is fairly uncommon and probably affects less than 1 percent of the population, we're talking about a serious problem," Dr. Joseph Coyle, a professor of psychiatry and neuroscience at Harvard Medical School in Boston who was not involved in the new research, said to HealthDay. "This is not about keeping a few extra newspapers in the house. This is about filling your house up with things to the point when you can no longer even live in it. And this study goes a long way towards helping us better understand how and why this happens."