Research Publications

Effect of environmental clutter on attention performance in hoarding

Many clients with hoarding disorder (HD) experience problems with paying attention, and they are often easily distracted during efforts to declutter their home. On the other hand, on standardized tests of attention, clients with HD obtain scores in the average range (showing no impairment). This mismatch between clients’ report of their problems and their test results raised the question of whether being in a distracting, visually complex environment makes it more difficult for people to maintain their attention. In this study, researchers randomly assigned 162 participants to complete standardized attention tests in either a standard clinical testing room (free from distractions) or a room that was set up to resemble a hoarded home. Participants completed a diagnostic interview, self-report questionnaires, and several neurocognitive tests of attention, which looked at their ability to pay attention when looking at something (i.e., visual attention) and when listening (i.e., auditory attention). Half of the participants did these tests in the standard clinical testing room, and the other half did them in the cluttered room (representing a Clutter Image Rating of about 4 out of 9.).


Our results found a strong correlation (r = 0.68) between the severity of participants’ self-reported hoarding symptoms and their self-reported attention-deficit/hyperactivity disorder (ADHD) symptoms. That is, participants with worse hoarding symptoms also had worse ADHD symptoms. The 61 participants who were diagnosed with hoarding disorder reported much higher ADHD symptoms compared to 55 healthy control participants (with no current psychological disorder). In comparison with the healthy control participants, those with hoarding were more likely to become distracted during longer (i.e., more boring) pauses between test items. Participants with hoarding also made more mistakes during tasks that require attention, and they scored lower on tests of auditory attention and working memory. These effects, however, were quite small compared to the effect size for self-reported ADHD symptoms.

Although we had expected that the cluttered room would interfere with attention, results showed that this was not true. Based on these results, future research should see if clients with HD are less persistent at trying to maintain attention when they are bored or in a bad mood.

Neurocognitive functioning in hoarding disorder

Clients with hoarding disorder (HD) describe symptoms such as problems with maintaining attention, trouble remembering things without a written reminder, and buying or collecting things impulsively. Research on these problems has not yet been able to find consistent results, possibly because different researchers use different kinds of tasks to measure cognitive functioning. On top of that, researchers usually use mental tasks that require multiple cognitive functions. For example, a student who is texting during a math lesson will not be able to remember a formula written on the board because they did not pay attention to it. Being able to remember something depends not only on memory ability but also on attention. (You have to notice something to be able to remember it.) To understand whether hoarding is related to cognitive functioning, this study used several overlapping measures of attention, memory, and executive function (which includes things like forming ideas, planning ahead, and using self-control). We recruited 178 adults who completed neuropsychological tests, a diagnostic interview, and questionnaires.


We compared 61 participants with HD and 55 healthy control participants (with no current psychological disorder) on 53 different measures of neurocognitive function. Analyses showed few differences between the two groups, and those few differences did not line up with the other findings from this study or from previous studies. No cognitive functioning factor was statistically associated with severity of hoarding symptoms. We concluded that individuals with HD do not show consistent deficits on tests of attention, memory, or executive function, compared to controls. Given these findings, we believe clients with HD may be worried about their cognitive abilities, such as attention, even when their cognitive abilities are completely normal. Another explanation is that deficits in cognitive performance may only come about when individuals are under emotional stress, such as when they need to make decisions about their belongings while organizing their homes.

Future research should look into clients’ subjective ratings of their personal cognitive abilities as well as how well they perform on cognitive tests when they are under emotional stress.

Hoarding symptoms correlate with the endowment effect

Researchers believe that people who hoard judge the value of objects differently than people who do not hoard. These “distorted” judgments about how much things are worth lead to excessive acquisition (collecting too many items) and difficulty discarding (struggling to get rid of stuff). However, people who hoard are not the only ones who make distorted judgments about objects. The endowment effect has been defined as valuing an object that you own higher than you would value the same object if it were owned by someone else. This effect is very commonly observed in the general population. To show this effect, researchers randomly assign different research participants to be either “owners” or “buyers” of the same item. Across many studies, “owners” often ask for nearly three times more than “buyers” are willing to pay. We wanted to test whether people with hoarding disorder would show an exaggerated endowment effect, so we conducted two studies using very different research methods. We recruited research volunteers with hoarding disorder and volunteers who said they do not have any mental health problems for each study.


In both studies, the hoarding and healthy control groups showed a similar endowment effect, which is not what we expected to find. However, we did observe that the size of the endowment effect was correlated to participants’ self-reported emotional difficulty with discarding objects, which is the key feature of hoarding. The size of the endowment effect was also correlated with the overall severity of hoarding symptoms – those with more intense hoarding symptoms also tended to show a greater endowment effect. In one of the studies, hoarding participants took part in specialized group cognitive-behavioral therapy. While participants’ hoarding got better during therapy, the endowment effect stayed the same. The therapy aimed to help clients change their judgments about the value of their belongings, but it did not specifically try to change the endowment effect.

Overall, our results suggest that future research should try to better understand the endowment effect in hoarding. Specifically, it should look at whether therapy can be used to decrease the endowment effect.

How can cities tackle hoarding?
Examining an intervention program bringing together fire and health authorities in Vancouver

Severe hoarding behaviour can become a public safety concern by increasing the risk of fire, making it difficult to control bugs and pests, and creating unpleasant odours. To deal with these risks – especially in apartment buildings where neighbours have shared walls – communities across North America have started using a harm reduction approach. This approach recognizes the mental health aspect of hoarding and prioritizes the care of the resident in the home. This study describes the implementation and outcomes of the Hoarding Action Response Team (HART), the City of Vancouver’s partnership between its fire prevention and public health services that was formed to address public safety issues associated with hoarding. Using data collected from 2016 to 2018, including health records, dwelling inspection reports, and notes from case briefings, this paper described the HART intervention model, provided statistics on the cases and interventions used, and examined predictors of both more severe clutter and better outcomes.


During the study, the HART team received 192 referrals and visited the homes of 143 clients. Of those 143 clients, only 82 met the team’s criteria for service. Most clients were referred to HART by housing providers or health and social service providers, but a few clients referred themselves for assistance. Most clients were older adults who lived in multi-family buildings. After an average of 9 months of engagement with the team, 65% of clients met their harm reduction goals. When the team finished working with a client, the amount of clutter in their home was about 2.6 points lower on the Clutter Image Rating scale. The team faced multiple obstacles, including limited resources and clients who avoided them. For various reasons, including clients withdrawing their voluntary participation, the team was unable to finish working with roughly 20% of clients, the vast majority of whom were people who owned their homes.

How well do hoarding research samples represent cases
that rise to community attention

A lot of what we know about hoarding comes from people with lived experience of hoarding who volunteer for treatment or research studies at universities, but hoarding also comes up in community settings. Many cases of hoarding are hidden in private until the situation becomes extreme, at which point professionals from many different organizations, such as housing providers, fire prevention, or public health agencies, become involved. We wanted to find out how people who volunteer for university-based research compare with those who get help in the community. In this study, we used existing data from three different research groups as well as case file data from three different community organizations to see how well research samples represent cases of hoarding that receive assistance in the community.


We analyzed data from 824 people with hoarding, and we found some key differences between those who volunteered for research and those whose hoarding became the focus of community-based interventions. Clients served by hoarding service providers are usually older, more often single and male, and usually have lower socioeconomic status. They are less likely to have good or fair awareness of the severity of their hoarding behaviour and its potential risks. Clients of hoarding service providers also have more clutter and more problems with things like poor sanitation, fire hazards, or fire safety in their homes. More clutter in the home was a strong predictor of these problems, but demographic variables (such as age or socioeconomic status) were not. Even after taking clutter volume into account, the homes of community-based clients were more likely to have poor sanitation.

These findings suggest that some aspects of hoarding research done in universities might not accurately reflect hoarding as it is encountered by community agencies.

Coordinated community-based hoarding interventions:
Evidence of case management practices

Hoarding is a complex issue that requires many different professional skills and resources to handle. This is especially true for severe cases involving complex mental health issues, a lack of insight, and public health and safety concerns, which demand a community-wide response. Case management approaches are commonly used to provide a range of social services to vulnerable and often marginalized people who are dealing with problems such as serious mental illness, domestic violence, or substance abuse disorders. These complex conditions often require professionals from different fields to work together closely with clients over an extended period of time. Social service staff play a key role in coordinating various services to help stabilize challenging situations related to health, mental well-being, or unstable housing. Because hoarding cases are complicated and require the expertise of many professionals, coordinated case management approaches may be especially useful for tackling hoarding. This study employed qualitative methods to examine the use of case management approaches in four community-based intervention models in North America.


Although only two out of the four sites used the term “case management” to describe their process for dealing with hoarding, we found that all sites took actions consistent with a case management approach.  The interventions used for hoarding cases aligned closely with eight key functions of case management: case finding, establishing and maintaining a supportive relationship, assessment, goal setting, arranging or linking with referrals for services, teaching or modeling, monitoring, advocacy, and crisis intervention. The availability of resources at each site influenced which specific case management activities were used the most. Case management appears to be a valuable approach for addressing complex social and functional problems experienced by urban clients with hoarding disorder.

Squalor in community-referred hoarded homes

Having a lot of clutter can make it hard to keep a home clean and can also prevent basic maintenance tasks. Poor sanitation, which is distinct from hoarding, is defined as an unhealthy level of uncleanliness. This would include pest infestations, rotting food, or feces or urine in the home. Available research suggests that poor sanitation is more common among hoarding cases than in the general population, but little is known about circumstances leading to unhygienic conditions in hoarded homes. This study aimed to learn more about what predicts poor sanitation in hoarding by looking at records from 381 cases seen by community agencies who help clients with hoarding and poor sanitation in Boston (Massachusetts), Hamilton (Ontario), and Vancouver (British Columbia). From 2010 to 2014, service providers from these agencies regularly visited homes to assess their conditions and check on the needs of the residents.


One agency that helped older adults at risk of self-neglect (average age of clients at this agency was 70 years) had a high percentage (72%) of clients with poor sanitation in their home. On the other hand, in a different agency that worked with low-income residents at risk of eviction, only 35% of homes had poor sanitation. Across all sites, having a lot of clutter was the only aspect of hoarding that was linked to poor sanitation. Furthermore, poor sanitation was more likely if conditions in the home (often a high volume of clutter) made it difficult to use the kitchen or bathroom, such as broken plumbing or blocked access. At one agency, clients who didn’t realize the seriousness or consequences of their hoarding behavior (also called poor insight) were more likely to have poor sanitation, but this was not replicated at the other two agencies. Contrary to what we expected, the number of pets didn’t significantly predict poor sanitation, although the situation might be different with animal hoarding. (This study involved only object hoarding, not animal hoarding.) This research provides a window into the homes of people who struggle with problematic living conditions and potential risk factors for unhygienic conditions in cases where hoarding is present.

Examining the role of fire prevention on hoarding response teams:
Vancouver Fire and Rescue Services as a case study

In hoarding situations, fire prevention officers are concerned about the risks of fire to residents in the home and to those in nearby homes, as well as the risks to emergency responders. An extreme buildup of combustible materials like papers and clothing not only prevents a quick escape but also increases the fuel load, causing fires to grow and spread much faster. While fire departments are responsible for enforcing fire codes, officers often lack the expertise to address the complex mental health challenges associated with hoarding. This case study highlighted the role of Vancouver Fire and Rescue Services in the City’s coordinated hoarding response, and outlined their protocol for fire inspections in hoarding cases. The study also compared complaint-driven hoarding inspections with standard annual fire inspections at restaurants.


Ensuring fire safety in hoarding cases is more challenging and time-consuming compared to standard yearly fire inspections at restaurants. About 20% of hoarding complaints did not involve any fire code violations. In many cases (about 45%), fire officers only needed to take informal actions for residents to agree to address the problem voluntarily. These informal actions included scheduling re-inspections to create a deadline and ensure that residents are accountable for making progress towards meeting the fire code. In remaining cases, fire officers needed to legal action to enforce the fire code. Reaching fire safety in hoarding situations, while also balancing other important concerns like tenancy preservation, requires specialized training for fire prevention officers.

The Vancouver Fire and Rescue Services hoarding team developed clear procedures for meeting the needs of people with disabilities, formed relationships with professionals from other community agencies, and followed guidelines for using discretion in enforcing fire codes. Although this approach requires investment and collaboration with other community agencies, it provides a valuable model for other regions to follow.

How much of too much?
What inspections data say about residential clutter as a housing problem

Housing providers have a responsibility to maintain properties and follow fire safety regulations. The 2010 Wellesley fire in Toronto started in a unit with a large amount of clutter, making it difficult for firefighters to put out the fire. As a result, 1,200 residents lost their homes, and many of them were later awarded compensation for lost property and injuries. When the building was later inspected, 19 out of 712 units (2.7%) were found to be “overcrowded with belongings”. Without research data on how common this level of residential clutter is, it is impossible to tell whether this is a big number or if this is typical for the small units that are usually available in low-income housing. In this paper, we used data from property inspections in Vancouver to estimate the size of the housing problem that comes from residential clutter and recorded the ways that municipal regulations document and address the problem.


We found that residential clutter is often considered a problem in marginal housing for vulnerable tenants. Based on our estimates, roughly 7% of single-room occupancy (SRO) housing units were identified by inspectors as having too much clutter. This suggests that problematic clutter happens in residential settings more frequently than what is reported in any published public health studies on rates of hoarding. The size of the problem varied across buildings, with some buildings having no cluttered rooms while others had up to one-third of occupied units affected by clutter. Larger buildings (more than 50 units) and those managed as social housing were more likely to have many units with problematic clutter. Over time, the amount of problematic clutter in a building stayed roughly the same, even when different inspectors were involved.

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