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Compulsively collecting animals, like these dogs rescued by Costa Rica’s Department of Animal Health, could be a unique mental disorder.

Kent Gilbert/AP Images for The Humane Society of the United States

Animal hoarding is its own mental disorder, study argues

We can all be packrats at times, letting our homes overflow with junk. But for millions of people, the compulsion to hoard things is a debilitating disorder—and when those “things” are animals, the results can be tragic. Now, a new study suggests the motivations and complexities behind animal hoarding are different enough from other kinds of hoarding that it ought to be classified as a wholly different type of mental disorder.

Not all researchers are convinced. “I think the arguments are interesting, but I don’t think they justify considering it distinct just yet,” says Graham Thew, a clinical psychologist who studies hoarding behavior at the University of Oxford in the United Kingdom.

For years, hoarding—thought to affect about 1.5% of people worldwide—was listed as a subtype of obsessive-compulsive disorder (OCD) in the Diagnostic and Statistical Manual of Mental Disorders (DSM), the global “gold standard” for identifying mental health conditions. Yet most hoarders don’t seem to share OCD’s persistent preoccupation with objects, which they forget and ignore after collecting. And medications generally effective for OCD don’t seem to work for people with hoarding disorder. So the DSM’s governing body reclassified it as its own entity in 2013, with animal hoarding as a subtype.

Elisa Arrienti Ferreira, a doctoral student at the Pontifical Catholic University of Rio Grande do Sul (PUCRS) in Porto Alegre, Brazil, was studying animal hoarding for her master’s degree thesis when it occurred to her that the condition—in which people compulsively collect stray cats, dogs, or other small creatures (and often fail to care for them properly)—might also deserve a separate designation. The motivations of animal hoarders—and their potential treatments—seemed to be sufficiently different from other hoarders.

So she and her adviser, PUCRS clinical psychologist Tatiana Quarti Irigaray, along with other colleagues, visited the houses of 33 adults who hoarded animals in Porto Alegre, assessing their living situations and interviewing the hoarders about their backgrounds and habits. On average, the hoarders had about 41 animals each, with dogs and cats being the most prevalent. A few of the adults also hoarded ducks. Seventy-five percent were considered low-income, 88% weren’t married, and 64% were elderly—so far consistent with generalized hoarding disorder.

But differences emerged, too. Whereas generalized hoarding disorder seems to affect men and women equally, 73% of the animal hoarders in the study were women. And although the DSM’s description of animal hoarding disorder states that most animal hoarders also hoard objects as well, Ferreira and Irigaray found that only about half of the hoarders in her study hoarded both animals and objects, they report in Psychiatry Research. The team’s interviews revealed that hoarders tended to start collecting their animals after a big disaster in their lives—the death of a child or the loss of a job, for example—a characteristic also not shared with generalized hoarding disorder.

Ferreira says these patterns suggest a different motivation for animal hoarding than object hoarding. “They think they are like missionaries, that they are saving these [animals’] lives … and that they are the only ones who can care for them,” she says. “When you speak to someone who is hoarding objects, they don’t say things like that. Instead, they say they are keeping things because they think they might need them someday.”

The practicalities of dealing with animal hoarding are also different than object hoarding. You can hire a company to haul junk away from a house, but removing, rehousing, and, in some cases, euthanizing animals is a much more complex—and more emotionally taxing—process, Ferreira says. “You have to think about where they will go.”

Although hers is only a small pilot study, Ferreira says the results raise the notion that animal hoarding might one day be reclassified as its own mental disorder. Such a move could motivate researchers to more diligently investigate its underlying neuropsychology, its triggers, and its potential treatments, she says.

Thew says more work is needed before others in the field can take the idea seriously. “The fact that animals are animate could mean the bonds are different, but this is only a hypothesis … and we don’t yet have any studies examining this specifically,” he says. “This paper makes some interesting behavioral observations, but I think we’d need more evidence of a distinct underlying psychological difficulty before we start to think about animal hoarding as a distinct difficulty.”