Jill, a 60-year-old woman in Milwaukee, has overcome extreme poverty. So, now that she has enough money to put food in the fridge, she fills it. She also fills her freezer, her cupboard and every other corner of her home. "I use duct tape to close the freezer door sometimes when I've got too many things in there," she told A&E's Hoarders. Film footage of her kitchen shows a cat scrambling over a rotten grapefruit; her counters—and most surfaces in her home—seemed to be covered with several inches of clutter and spoiled food. "I was horrified," her younger sister said after visiting Jill. And the landlord threatened eviction because the living conditions became unsafe.

Jill joins many others who have been outed on reality TV as a "hoarder." We might have once called people with these tendencies "collectors" or "eccentrics." But in recent years, psychiatrists had suggested they have a specific type of obsessive-compulsive disorder (OCD). A movement is underfoot, however, for the new edition of the psychiatric field's diagnostic bible (the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, or DSM-5), to move hoarding disorder to its own class of illness. And findings from a new brain scan study, published online August 6 in Archives of General Psychiatry, support this new categorization.

Hoarding disorder is categorized as "the excessive acquisition of and inability to discard objects, resulting in debilitating clutter," wrote the researchers behind the new study, led by Yale University School of Medicine's David Tolin.

Many of us might feel our homes or workspaces are far more cluttered than we would like—or than might be good for our peace of mind. But those with diagnosed hoarding disorder usually have taken this behavior to a different level. The Mayo Clinic even has a guide for treatment and prevention of hoarding disorder. One recommendation they provide: "Try to keep up personal hygiene and bathing. If you have possessions piled in your tub or shower, resolve to move them so that you can bathe."

Some people hoard particular types of things, such as newspapers, craft supplies or clothing. Others, with a condition known as Diogenes syndrome, keep trash, including old containers, rotting food or human waste. Finally, as Animal Planet's Animal Hoarders has shown, many hoarders collect more pets than they can appropriately care for, risking both their own and their animals' health and safety.

To find out more about how the brains of hoarders might actually differ from those of healthy adults—and potentially even those with OCD—Tolin and his colleagues recruited 43 adults with a diagnosed hoarding disorder, 31 with OCD and 33 healthy adult controls to undergo fMRI brain scans. Each subject was asked to bring in a stack of miscellaneous, unsorted papers from their home, such as newspaper and junk mail. A similar collection of paper items from the experimenters was intermingled. Fifty items belonging to the subject and 50 items belonging to the experimenter were scanned and projected into the subject's field of view in the fMRI. Subjects were asked to choose whether they wanted to keep a displayed item (either belonging to the subject or to the experimenters) or get rid of it by pressing a button. Afterward (and in a shorter pre-experiment training session), all of the discarded items were shredded right in front of them—ensuring that they knew that their decisions would have a real and immediate consequence.

Healthy controls chose to discard a mean of about 40 of the 50 items they brought. Those with OCD discarded about 37 items. But those with a hoarding disorder discarded only about 29 of the 50 things they brought. It also took hoarders slightly longer than healthy controls (2.8 seconds compared with 2.3 seconds) to make their decision about what to do with the items. And they reported substantially more anxiety, indecisiveness and sadness than healthy controls or those with OCD while making decisions.

Those with hoarding disorder showed key differences in the fMRI readings in both the anterior cingulate cortex, associated with detecting mistakes during uncertain conditions, and the mid- to anterior insula, linked to risk assessment, importance of stimuli and emotional decisions.

Interestingly, hoarders showed lower brain activity in these regions when they were deciding about other people's items. But when they were faced with their own items, these areas of the brain showed much higher rates of signaling than those in either people with OCD or the healthy controls. Those with hoarding disorder also reported "greater anxiety, indecisiveness and sadness" during the decision-making process than those with OCD or the healthy controls.

As Tolin and his co-authors noted, hoarders are not necessarily eager to keep everything they possess, but rather "the disorder is characterized by a marked avoidance of decision-making about possessions." And the extra activity in the anterior cingulate cortex and insula while evaluating what to do with their own items "may hamper the decision-making process by leading to a greater sense of outcome uncertainty," the researchers noted. In other words, hoarders might often feel that they are at risk of making a wrong decision—and that that decision could bring with it greater risk than it actually would. "The slower decision-making may be a central feature of impaired decision making in hoarding," the researchers noted.

The frequent theme on hoarder reality shows is that the individual does not realize that their lifestyle has spiraled out of control. Bernie, a 59-year-old Illinois woman featured on TLC's Truth Be Told: I'm a Hoarder said, "I don't consider myself to be a hoarder—not at all," even after showing the film crew an entirely full house and a pool table room piled nearly to the ceiling with toys and other collected items—and after her daughter and son had implored her to clean up her house. As the authors of the new paper note, those with the disorder "are frequently characterized by poor insight about the severity of their condition, leading to resistance of attempts by others to intervene." And as the Mayo Clinic notes, even if hoarders' collections are disassembled, they often begin acquiring more items right away because their underlying condition has not been addressed.

As with for patients with OCD, those with hoarding disorder have had some success reducing negative symptoms by taking selective serotonin reuptake inhibitors (SSRIs). Psychotherapy and cognitive-behavioral therapy are also frequently employed to help patients overcome the disorder. Although neither of these approaches is a sure-fire way to cure hoarding, the biggest hurdle to recovery still seems to be recognizing the problem. And as the Mayo Clinic recommends, "getting treatment at the first sign of a problem may help prevent hoarding from becoming severe."