Study: Hoarding Disorder Symptoms More Highly Comorbid with ADHD Than with OCD

January 12, 2024

Hoarding disorder (HD) is significantly more common in people with attention deficit hyperactivity disorder (ADHD) than it is in people with obsessive-compulsive disorder (OCD), according to a study published in the Journal of Psychiatric Research.¹

Researchers from the Brain Center Firenze in Italy and McMaster University in Canada found that adults with ADHD had a substantially Higher prevalence of hoarding disorder (32%) than did adults with OCD (8%) or adults in the control group (4%).

A similar pattern emerged during a second analysis focused on hoarding disorder symptoms of excessive clutter and difficulty discarding. Twenty-two percent of the ADHD group had the condition compared to 6% of the OCD group and 4% of the control group.

The American Psychiatric Association defines hoarding disorder as a distinct psychiatric condition characterized by persistent difficulty discarding possessions, regardless of their actual value, resulting in severely cluttered living spaces, distress, and impairment.

The APA classified hoarding disorder as a subtype of OCD in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) in 2013. However, more recent research has revealed that people with hoarding disorder don’t necessarily exhibit classic OCD symptoms. ²

The current study found that OCD patients with earlier age of onset showed Higher levels of ADHD symptoms in both childhood and adulthood, but this comorbidity did not significantly correlate with the presence of hoarding disorder symptoms. Participants with ADHD and hoarding disorder, however, exhibited more severe ADHD symptoms. The researchers identified inattention and impulsivity in the ADHD group and impulsivity in the OCD group as significant predictors of HD.

“Some studies have suggested that there may be some shared vulnerability between hoarding disorder and ADHD, and that inattentive ADHD may predict some of the core features of hoarding disorder,” Carolyn I. Rodriguez, M.D., Ph.D., professor, and director of the Translational Therapeutics Lab in the Department of Psychiatry and Behavioral Sciences at Stanford University school of Medicine, told ADDitude. “It’s important to have a careful assessment to determine if clutter motivates more hoarding behaviors or if inattention and other features of ADHD do.” ²

The main difference between an ADHD-clutter problem and a hoarding-clutter problem is that someone with hoarding disorder has a reason for saving items. “It’s not just a function of being unable to organize or unable to get your behavior together to get rid of things. There’s an actual reason why the person’s saving it,” said Randy O. Frost, Ph.D., the Harold Edward and Elsa Siipola Israel Professor Emeritus of Psychology at Smith College and co-presenter with Rodriquez of the ADDitude webinar “What Is Hoarding vs. ADHD Clutter? Defining Characteristics and Strategies to Help.”

The study involved 157 adults: 57 with ADHD, 50 with OCD, and 50 controls. More than half of the participants with ADHD (53%) and OCD (52%) were treating their conditions with medication. The study found no significant difference in hoarding symptoms between medicated and non-medicated patients.

According to the authors, this is the first direct comparison of HD prevalence in a sample of adults with ADHD, OCD, and healthy controls. They recommended more large-scale studies focusing on hoarding disorder’s link to ADHD and HD treatment, noting that this study had several study limitations, including a small sample size.

“Although HD is included in the DSM-5 in the obsessive-compulsive and related disorders chapter, in the last few years, HD has been consistently associated with ADHD,” they wrote. “A better understanding and definition of the boundaries between HD and the OCD and ADHD spectrum could lead to the development of a more precise treatment approach for hoarding disorder.”