A multitrait-multimethod matrix investigation of hoarding

• Convergent and discriminant validity of three hoarding domains were examined in a MTMM matrix.
• The three-factor model provided an adequate fit for the data.
• Convergent validities were high, but hoarding factors evidenced poor discriminant validity.
• Each factor discriminated hoarding from OCD patients and community controls.

Hoarding is a serious and potentially life-threatening mental health problem that, until recently, was considered a subtype of OCD. However, recent research suggests it is distinct and more prevalent than OCD. Three key defining features have emerged in factor analytic studies of hoarding scales: excessive acquisition, difficulty discarding, and excessive clutter. Covariation among these defining features has received limited attention. The primary aim of the current study was to examine the role of the three key features in defining hoarding disorder. Convergent and discriminant validity of the three hoarding factors were examined in a multitrait-multimethod matrix. A secondary aim was to examine the extent to which each hoarding feature distinguished individuals meeting criteria for hoarding from those with OCD and community controls. Although the three-factor model provided an adequate fit for the data and convergent validities were high, the hoarding factors evidenced poor discriminant validity across measures. The findings provide preliminary support for a more parsimonious merging of the clutter, acquisition, and discarding subscales versus parsing out subscale scores. Specifically, the active acquisition of items, buildup of clutter, and difficulty discarding accumulated possessions co-occurred strongly enough to be considered a unidimensional construct. Thus, these symptoms were less attributable to separate phenomena and better conceived as part of a cohesive hoarding phenotype. Each of the three factors discriminated hoarding participants from OCD patients and community controls, but did not discriminate the latter two groups. The findings have implications for treating acquisition as a specifier in DSM-5.