The complex clinical and cognitive phenotype of adult patients with attention deficit hyperactivity disorder (ADHD) and comorbid hoarding disorder.

Objectives: Several studies consistently showed that patients with attention deficit hyperactivity disorder (ADHD) have high rates of hoarding disorder (HD) comorbidity. The aim of the present study was to compare the clinical and cognitive features of adult ADHD patients with and without hoarding comorbidity according to a self-report measure, and a sample of healthy controls.

Methods: Fifty-seven consecutive adult outpatients with a primary diagnosis of ADHD with comorbid hoarding disorder (ADHD+HD), 57 matched ADHD patients without hoarding disorder comorbidity (ADHD-HD), and a control group of 47 healthy controls (HCs) were enrolled. All subjects undergone a comprehensive clinical assessment and a neurocognitive assessment focused on attention, memory, and executive functions.

Results: The ADHD groups differed on most of the clinical and cognitive measures compared to HCs. ADHD+HD patients showed similar ADHD symptoms but greater subjective impulsivity, mood and anxiety symptoms, and a greater functional impairment compared to ADHD-HD patients as well as greater attentional and executive functioning impairments.

Conclusions: ADHD patients with comorbid hoarding disorder present a more complex clinical and neuropsychological phenotype correlated to a greater functional impairment compared to ADHD patients without this comorbidity. These results further highlight the relevance of assessing and treating hoarding behaviours in adults with ADHD.