Odor memory, but not odor identification, is impaired in children with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is one of the most common, highly inheritable childhood-onset psychiatric disorders. Previous research indicated that individuals with ADHD may experience altered olfactory function, but the results were inconsistent. The present study compared odor identification and odor memory abilities between 51 children with ADHD and 51 healthy controls. Odor identification ability was assessed using the U-Sniff test, and odor memory ability was evaluated using a modified version of the U-Sniff test. The ANCOVA results showed no significant difference in odor identification. However, children with ADHD had significantly lower hit rates in odor memory, with no differences in false alarm rates or hits-false alarms. We found a significant correlation between the hit rate in odor memory and the scores on the Children's ADHD Behavior Rating Scale, the Swanson, Nolan, and Pelham-IV Rating Scale (SNAP-IV), the Inattention subscale of the SNAP-IV and the Hyperactivity Index of the Conners Parent Symptom Questionnaire. These findings indicate that olfactory memory might be impaired in children with ADHD, providing a potential behavioral marker for assessing the impact of the disorder on cognitive functions.