Day after day, year after year, Patrice Moore received a load of mail—newspapers, magazines, books, catalogs, and random solicitations. Each day the 43-year-old recluse piled the new with the old, until floor-to-ceiling stacks of disorganized paper nearly filled his windowless 10-by-10-foot apartment in New York City. In late December, the avalanche came, and Moore was buried standing up. He stood alone for two days, until neighbors heard his muffled moaning. The landlord broke in with a crowbar; it took another hour for neighbors and firefighters to dig Moore out and get him medical help.

Newspaper accounts of the avalanche duly noted that Moore was luckier than Homer and Langley Collyer, two pack-rat brothers who for four decades crammed their Harlem mansion with heaps of debris: newspapers, old Christmas trees, sawhorses, perhaps a dozen pianos, even a dismantled automobile. On March 21, 1947, Homer was found dead of starvation. It took another 18 days for city workers to uncover Langley’s smothered body.

Scientists long assumed that compulsive hoarding is simply a symptom and a subset of obsessive-compulsive disorder. But new studies suggest it may be a distinct disorder with its own unique signature in the circuitry of the brain. The ongoing research has taken on a certain urgency as cities across America have set up task forces to help landlords and relatives deal with thousands of people like Moore whose health is endangered by their compulsion to stockpile.

That compulsion, scientists now theorize, is a natural and adaptive instinct gone amok. Elsewhere in the animal kingdom, the instinct to hoard offers clear evolutionary advantages. One of the most avid hoarders is the Arctic gray jay. To ensure that it has enough food for the long, dark winter, the bird caches over a wide area some 100,000 mouthfuls of berries, insects, and spiders, says Tom Waite, a biologist at Ohio State University in Columbus. Hoarding may also function as a mating strategy. Male black wheatears, avian residents of dry and rocky regions of Eurasia and Africa, spend considerable time and energy piling up heavy stones before mating season. Those with the largest piles are more likely to mate. “It’s called resource-holding potential, and it’s a way of advertising to a mate your true Darwinian fitness,” Waite says.

Humans appear to be the only species that takes hoarding to pathological excess. In extreme cases, compulsive hoarders may fill their houses so full of stuff that they can no longer use the bed, the table, or even entire rooms. They can’t invite friends over. They can’t keep track of their bills. They can’t organize themselves sufficiently to hold a job. As they age and their memories fade, they may no longer even remember what they’ve been hoarding. One 61-year-old man who attends the Clutter Workshop, a support group in Hartford, Connecticut, gathered so many books, papers, and pieces of junk mail that he filled as much of the house as his wife would tolerate. Somewhere in there he lost a six-figure check for the sale of his parents’ house. “You can’t imagine my total embarrassment at having to call the attorney and ask for a new one,” he says.

How widespread is the disorder, and why is it so acute in certain individuals? Answers are hard to gather in part because hoarders tend to be secretive about their habits. Nonetheless, researchers have identified various interesting patterns. For example, hoarding often runs in families. “People with this problem tend to have a first-degree relative who also does,” says Randy O. Frost, a psychologist at Smith College. “So it might be genetic, or it might be a modeling effect.”

Hoarders tend to be emotional; they attach sentimental value to most of their belongings, even used paper coffee cups or outdated calendars. “They’re thinking about all their stuff the way you think about the contents of your jewelry box,” says Nicholas Maltby, a psychologist who works with compulsive hoarders at the Institute of Living in Hartford. Hoarders are often intelligent and well educated, and they typically think in complex ways. “They may have more creative minds than the rest of us in that they can think of more uses for a possession than we can,” says Frost.

Most fundamentally, scientists say, hoarders possess a profound inability to make decisions. Frost describes combing through the possessions of one patient and coming across an article from a travel magazine. The patient could not decide whether to throw away the article or, if she kept it, whether to file it under “travel” or one of the various countries it discussed. So she made several copies and put one in each category.

Indecisiveness extends to other areas of hoarders’ lives. They cannot decide what they should be doing, so on any given day they may start a dozen different projects. “They bounce from one thing to another,” says Sanjaya Saxena, a professor of psychiatry at the University of California at Los Angeles. They also have trouble deciding how much to say. “They are overtalkers. They have to give you every possible detail, rather than a simple answer to a question.”

Compulsive hoarding, unlike obsessive-compulsive disorder, does not respond to treatment with antidepressant drugs, and unlike sufferers of obsessive-compulsive disorder, hoarders actually enjoy being surrounded by all their stuff. “Hoarding seems to be more like compulsive gambling or compulsive shopping because it’s pleasurable to the person,” Maltby says. Moreover, positron-emission tomography brain scans indicate that hoarding and obsessive-compulsive disorder may be quite distinct. In a study published in the June American Journal of Psychiatry, Saxena reported that hoarders have lower activity in the cingulate gyrus—a structure that runs through the middle of the brain, front to back—particularly in areas known to be involved in decision making and focusing attention. People with obsessive-compulsive disorder who are not hoarders do not exhibit this characteristic at all; their brains, in contrast, show elevated activity in areas that generate concerns about danger, contamination, and order.

Saxena’s findings are corroborated by a recent study from the University of Iowa, involving a group of people who had suffered lesions in various parts of their brains as a result of strokes or other neurological diseases. Thirteen patients had never shown a tendency to hoard until they suffered lesions in the mesial frontal region—which encompasses the anterior cingulate gyrus—at which point they fell victim to what the scientists described as a “massive and disruptive accumulation of useless objects.”

The findings suggest that doctors may want to look outside the realm of obsessive-compulsive disorder for drug treatments for hoarding, Saxena says. He plans to experiment with stimulants typically given to people with attention deficit disorder. “We’ll try Ritalin and also drugs that seem to improve cognitive functioning in people with Alzheimer’s,” he says. “The goal would be to improve attention and concentration and find out whether that helps hoarders.”

In the meantime, Frost and Gail Steketee of Boston University are working to develop an effective cognitive-behavioral treatment. Three different behaviors must be addressed, Frost says: the organization of stuff, the acquisition of new stuff, and most important, the timely discarding of stuff. The researchers are developing a

treatment model that calls for six months of therapy in which patients articulate their mental struggle as they try to discard some of their possessions.

Maltby agrees that hands-on therapy—helping hoarders analyze their thoughts as they sift through their stuff—is crucial. “The problem isn’t solved by cleaning. It’s not solved by coming in and throwing out the hoarders’ stuff. They can collect it again. You have to solve the problem at the decision-making level.”