Look around my house, and you will find some weird stuff.

I can justify a few pieces of my collection. The small tribe of kachina dolls and the menagerie of wooden African animals, for instance, have their aesthetic merits. My interest in pharmacology has spawned a personal museum of mortars, pestles and old medicine bottles. But then I think about other things I cannot bring myself to throw out: old squash and tennis rackets, unread magazines from the last century, and piles of T-shirts on the verge of disintegration. I also hold on to old coffeemakers. I have to admit, that just seems a bit nutty.

Lucky for me--and a lot of other people--it is not the content of a person's closets that defines what psychologists would call a "problem" with collecting. It is the amount of clutter and its consequences. Although accumulating stuff can be expensive and the objects sometimes take up a good bit of space, most people do not run into trouble. They do not spend more money than they can afford, nor do they allow the stuff to take over essential living space. But the urge to hang on to things can go awry. And when it does, the consequences of this hoarding may be severe.

Hoarders have intrigued artists, scientists--and even talk show hosts. Oprah Winfrey dedicated a show in May 2005 to hoarding, featuring a woman named Kathryn who collected 81 cats and six dogs--along with a second woman, Krista, who crammed her four-bedroom house with mounds of clothes and junk. Although hoarders have long been subjects of fascination, it is only recently that researchers and clinicians have begun to warn that an unhealthy compulsion to stockpile may afflict more than a million people in the U.S. alone. And now a handful of neurologists, psychiatrists and psychologists have started to identify the underpinnings of the condition and have come up with a promising treatment.

People afflicted with this problem acquire and are unable to discard large numbers of items. According to Randy O. Frost, a psychologist at Smith College, what distinguishes the illness from normal collecting is the extent to which the hoarder's stuff takes over his or her living space and the impairment that is produced by the relentless collecting.

The most commonly saved items include newspapers, old clothing, bags, books, mail, notes and lists. These items can accumulate to the extent that space is no longer available for essential activities such as cooking, sleeping and bathing. Frost points out that the harmful consequences range from failure to pay bills (they get lost in the clutter) to injury and even death when a pile of refuse topples over. The most clinically severe end of the hoarding continuum is dubbed the Diogenes syndrome, after the Greek philosopher who lived in a barrel. In this syndrome, severe self-neglect and a refusal to accept help accompany hoarding, resulting in nutritional deficiency and other health problems.

Collecting Data
Hoarding is explicitly mentioned in the "bible" of psychiatry, the American Psychiatric Association's Diagnostic and Statistical Manual (DSM-IV), as a symptom of obsessive-compulsive personality disorder (OCD). It is seen also in a raft of other conditions, including traumatic brain injury, tic disorders such as Tourette's syndrome, mental retardation and neurodegenerative disorders. But some experts have started to argue that hoarding should be considered a syndrome or entity in its own right. To begin with, hoarding can crop up in the absence of any other pathology and result in severe impairment. Some evidence also indicates that hoarding is more common than is generally recognized.

Frost and his associates surveyed public health departments and found that over a five-year period they received only 26 complaints of hoarding per 100,000 people. He believes this figure seriously underestimates the prevalence of the problem. He points out that the condition in which hoarding appears most frequently is OCD and that it afflicts 20 to 30 percent of those patients. Given that OCD occurs in about 1 to 2 percent of the world population, this would put the prevalence of OCD-related hoarding at about four per 1,000.

In addition, a study by Jen-Ping Hwang and his colleagues in the department of psychiatry at Taipei Veterans General Hospital found that 22.6 percent of hospitalized patients with dementia engaged in clinically significant hoarding, and Dan J. Stein in the department of psychiatry at the University of Stellenbosch in Cape Town, South Africa, found that patients in a geriatric psychiatry inpatient unit displayed a hoarding prevalence of 5 percent. Stephen Salloway, director of neurology and the Memory and Aging Program at Butler Hospital in Providence, R.I., estimates that about 5 percent of the dementia patients he sees exhibit clinically significant hoarding. Based on the extent of the disorder found in such sample populations, Sanjaya Saxena of the University of California, San Diego, estimates that there are one million to two million hoarders in the U.S. alone. He considers hoarding a major public health problem.

One misconception about the condition is that it must arise from highly aberrant psychological processes or brain activity. In fact, similar behavior is common and highly conserved across a wide variety of species. In humans, clinically significant, compulsive gathering that results in impossible clutter appears to be on a continuum with "normal" collecting and the universal tendency to hold on to clothes, books and other items far beyond the point that they are used or needed. In some situations, excessive storing may even be useful. For example, in times of war or in other situations when supplies of food, medicine and other crucial supplies might be limited, people accumulate goods.

Similarly, much of what is called hoarding in animals is adaptive and has a clear purpose. Animal research has focused on food hoarding, but birds and other animals also collect aluminum foil, beads and other brightly colored objects, sometimes as a part of mating behavior. Some hoarding behavior in animals, however, does not seem to be purposeful and is more like the pathological kind seen in humans--collecting as an end in itself. Normal rats are known to stockpile food seemingly for the sake of it, without regard to how much they already have, and given the choice, hamsters prefer keeping additional glass beads to food.

Animal studies have also revealed a complex set of controls on this behavior. Chemical mimics of the neurotransmitter dopamine stimulate food hoarding in rats, whereas analogues of another neurotransmitter, serotonin, reduce it. Sex hormones and opiates also modulate this activity. Genetic research points to the importance of brain chemistry as well. Patients who hoard are more likely than a typical person to have close relatives with similar symptoms. Genetic analysis of hoarders with OCD and Tourette's syndrome has linked this compulsion to a specific form, or allele, of COMT--a gene that encodes an enzyme involved in the metabolism of dopamine and other neurotransmitters.

Electrical stimulation and lesion experiments in animals suggest that the drive to amass items comes from the brain's subcortical limbic system, made up of evolutionarily primitive structures that are involved in survival-related behaviors such as appetite, sexuality, aggression and emotional behavior. The onset of hoarding in patients with traumatic brain injury, stroke and neurodegenerative diseases has also helped pinpoint brain regions involved in this behavior. Saxena and his colleagues used brain imaging to study OCD patients with compulsive hoarding and showed they had lower metabolic activity in their limbic system.

Steven Anderson and his colleagues at the University of Iowa recently found that 13 out of 86 patients with brain lesions developed persistent hoarding behavior. In this case, though, all 13 had damage to the mesial prefrontal region, a part of the frontal cortex responsible for so-called executive, high-order cognitive functions. Salloway points out that patients with frontotemporal dementia, whose brains are damaged in the same region, are especially prone to hoarding. He suspects, as does Anderson, that the compulsion can arise when high-level circuits that normally inhibit this behavior are interrupted.

Healing Hoarding
Ultimately, a thorough understanding of the neural basis for hoarding could lead to better treatment. Any such advance would be welcome because the disorder has been notoriously difficult to treat. Both clinical trials and case reports show that compulsive collecting does not respond well to either the antidepressants or the psychotherapies that alleviate other OCD symptoms. Recently, however, Frost and his colleagues have developed a cognitive-behavioral treatment that addresses hoarding's various psychological motivations.

Some hoarders have difficulty discarding things because of their indecisiveness; others because of their emotional attachment to their possessions. As Frost points out, hoarders believe that their possessions are part of them: "They can't distinguish important from unimportant things." Whereas most people see a 10-year-old news magazine as trash, hoarders believe it holds critical information. Still others do not discard items because they suffer executive dysfunction and other cognitive deficits that make it difficult to organize their belongings and to distinguish between items they need and those they do not.

Frost's technique uses group therapy sessions to help patients identify the thoughts and emotions that sustain their behavior and then challenges the validity of these motivators. Patients are also encouraged to practice new patterns of behavior. They go on shopping excursions without buying anything, discard objects both in the group setting and as homework, and they learn methods for organizing their belongings. Preliminary results are promising. Patients treated in this manner begin to tolerate the anxiety associated with discarding objects and gradually reduce the extraneous junk filling up their homes. Not all the clutter has to be removed, just enough to reduce fire and health hazards.

Frost says that anyone working with these patients must remain mindful of the excruciating anxiety they go through at the mere thought--let alone act--of throwing out one of their things. A key principle is that the hoarder is the only one who should discard possessions. Attempts, however well meant, by family members or other caregivers to tidy up by tossing stuff out will alienate the patient and increase his or her isolation and resistance to any kind of intervention. Without some change on the hoarder's part, as soon as relatives, therapists or camera crews leave, the newspapers, mail, and assorted odds and ends will invariably pile up once again.