Results Summary

What was the research about?

People with hoarding disorder are unable to give or throw things away. They also often buy or collect items to excess. Clutter caused by hoarding can lead to unsafe living conditions and make it hard to function in daily life. Group cognitive behavioral therapy, or CBT, is one type of treatment for hoarding disorder. Patients meet in groups with others who have hoarding disorder and learn to change their patterns of thinking and behavior.

Some communities only have a few therapists trained in CBT. This lack of therapists can make it hard for people with hoarding disorder to get treatment. Peer-led group therapy is a type of treatment led by people who have or have had hoarding disorder and received training to help others. It gives people more opportunities to get treatment.

The research team wanted to see if peer-led group therapy worked as well as therapist-led CBT to treat hoarding disorder.

What were the results?

The study found that peer-led group therapy helped as many patients with hoarding disorder as therapist-led CBT did. One month after treatment ended, patients in both groups had fewer symptoms of hoarding disorder. They were also better able to do daily activities, such as preparing food or taking showers. Within one to two years after treatment, patients in both groups still had fewer symptoms of hoarding disorder but they did not maintain the improvements in daily activities.

Who was in the study?

The study included 323 patients with hoarding disorder in San Francisco, California. Of these patients, 75 percent were female. Sixty percent of patients were white, 11 percent were Asian, 8 percent were African American, and 20 percent were other or more than one race; 9 percent were Hispanic. The average age was 59.

What did the research team do?

The research team assigned patients by chance to one of two groups. One group took part in CBT led by therapists using a hoarding disorder therapy workbook as a guide. This group had 16 two-hour group sessions over 20 weeks. Patients in this group learned about hoarding symptoms. They also learned how to set goals and how to change their behavior and thinking.

The other group took part in peer-led therapy. Patients in this group had 15 two-hour sessions over 20 weeks. The group leaders had current or past hoarding disorder and received training to help others with hoarding disorder. They used a workbook that had similar activities to those of the CBT group.

The research team surveyed each patient about his or her hoarding disorder symptoms and daily activities. The team collected this information at the beginning of the study and within one month after the end of treatment. One to two years after treatment ended, the team followed up with patients in the study again.

What were the limits of the study?

About 30 percent of patients in the study didn’t finish treatment. The results may have been different if everyone completed the treatment. The findings from the study may not apply to patients with hoarding disorder who don’t want treatment or who are not aware of their hoarding disorder.

Future studies could look into improving both types of treatment and examine ways to encourage patients to complete the treatments.

How can people use the results?

It can be hard to find trained therapists to help with hoarding disorder. Peer-led group therapy was as effective as group CBT and may be a good option for making treatment available to more people.

Final Research Report

View this project's final research report.

Peer-Review Summary

Peer review of PCORI-funded research helps make sure the report presents complete, balanced, and useful information about the research. It also confirms that the research has followed PCORI’s Methodology Standards. During peer review, experts who were not members of the research team read a draft report of the research. These experts may include a scientist focused on the research topic, a specialist in research methods, a patient or caregiver, and a healthcare professional. Reviewers do not have conflicts of interest with the study.

The peer reviewers point out where the draft report may need revision. For example, they may suggest ways to improve how the research team analyzed its results or reported its conclusions. Learn more about PCORI’s peer-review process here.

In response to peer review, the PI made changes, including

  • Providing more detail about the analyses, particularly about how missing data were handled. Data were missing mostly because participants did not complete the follow-up assessment. The researchers did not believe it was appropriate to impute data for entire questionnaires so they did not account for missing data in their analyses of the primary outcomes. These analyses were conducted only for the 76 percent of randomized participants who provided follow-up, which raised concerns about how well the results reflect the study population as a whole.
  • Describing sensitivity analyses where the researchers reanalyzed outcomes for only those participants who completed treatment, in response to reviewers’ concerns about the effect of the high dropout rate from the intervention program.
  • Laying out the differences in the number and format of group sessions between the compared interventions. The researchers indicated in their response to reviewers that they did not believe there were material effects of these differences on the outcomes given their experience with these interventions in past studies.
  • Explaining why longitudinal follow-up assessments were added late in the study rather than being part of the original study protocol. The researchers added information to the report indicating that they obtained additional funding late in the study to complete the longitudinal analyses.

Conflict of Interest Disclosures

Project Information

Carol A. Mathews, MD*
Kevin Delucchi, PhD
The Regents of the University of California, San Francisco
Comparison of Peer-Facilitated Support Group and Cognitive Behavioral Therapy for Hoarding Disorder

Key Dates

September 2013
April 2018

Study Registration Information

*Carol A. Mathews, MD, who was at University of California, San Francisco when this project was awarded, is now at University of Florida.


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Last updated: March 14, 2024