Does Hoarding Have Evolutionary Roots?

On the surface, clinical hoarding has little to do with adaptation to the environment. A closer analysis, however, suggests that people who store too much stuff are motivated by self-preservation anxieties.

Hoarding in Nature

Many animals cache food for the winter and humans do the same in places with long, cold winters. Such hoarding is adaptive and solves the problem of food scarcity related to seasonal change in high-latitude geographies. For example, a buffalo hunter in North America may dry some of the meat to be consumed in winter.

Caching is common among birds and mammals. For example, the Clark's nutcracker bird is celebrated for its capacity to hide many thousands of seeds and retrieve them later, apparently from memory.

Smaller mammals, such as rodents, are highly vulnerable to winter cold, and many hoard food in secure hiding places. The mountain pika, a relative of rabbits, hoards grass. The more familiar chipmunk can be seen moving around with its cheek pouches packed with seeds and nuts on its way to subterranean caches.

Brain Pathology

The animal model of hoarding suggests that this behavior is a feature of our inherited brain biology. Hoarding is normally suppressed but emerges in the circumstance of brain pathology that disinhibits the activity.

Clinical hoarding often emerges in patients suffering from advanced Alzheimer's disease. People suffering from senile dementia commonly hoard food and keep food items well beyond their due date, creating a risk of unsanitary conditions. They may also compulsively arrange valued non-food items, investing them with a high level of emotional significance, possibly because social and familial relationships are undermined by dementia.

Hoarding is associated with functional deficits in the frontal and temporal lobes of the brain, particularly with problems in the left temporal lobe. Apparently, hoarding reduces anxiety in this clinical population.

Adaptive Accumulation of Money and Resources

According to the DSM-5, the defining characteristic of clinical hoarding is a persistent difficulty in discarding objects, regardless of their actual value. Problem hoarders accumulate materials that clutter up living areas and create hazards, such as difficulty in leaving the building in case of fire. These collections become a problem for hoarders themselves and interfere with their social lives and/or occupations.

Conversely, during economic downturns, people may hoard food and other materials for rational reasons.

In the DSM-5, hoarding is a separate diagnosis from obsessive-compulsive disorder, although hoarders may also have obsessive or compulsive features, including anxiety about discarding objects that are not particularly useful (a compulsion) and arranging them in specific ways (an obsession).

Whatever the semantic issues, hoarding reflects basic emotional insecurities, including the fear of being socially isolated.

Problem Accumulation and Emotional Insecurity

Senile hoarding likely occurs because memory problems rob the individual of normal social relationships. When that happens, they develop deep sentimental attachments to objects that become a source of comfort and security. These feelings are out of proportion to the actual value or usefulness of the possessions.

Similarly, non-senile hoarders may feel emotionally insecure, or socially isolated, and make disproportionate emotional investments in their collections of things.

Because the hoarder is sentimentally attached to objects, they have difficulty discarding any of them. As a result, they accumulate, cluttering up their living spaces, offices, and other places of work with deleterious consequences for their happiness and health.

Hoarding and Compulsive Shopping

There are many different kinds of collectors, and most of them are not pathological. For example, an art collection is likely to appreciate faster than real estate, so we can see art collection has a rational economic motive.

On the other hand, a collection of washers is unlikely to accumulate anything but rust. The collections of problem hoarders generally involve depreciating assets, whether it is stale food, expired medicines, or antiquated electrical equipment.

When objects acquire a sentimental value that is far in excess of their utility, there is a motive for accumulating them. Adding to the collection is a source of pleasure and motivates compulsive shopping.

In many cases, pathological hoarding consists not of organized collections but of a seemingly random melange of items that other people categorize as junk.

Junk or treasure, the problem is very disruptive to ordinary life. In the absence of professional help—whether from personal organizers or psychotherapists—hoarding generally gets worse over time.

Hoarding may have facilitated survival for our remote evolutionary ancestors, but is a very bad idea in our current environment of material excess.