An overactive mind: Investigating racing thoughts in ADHD, hypomania and comorbid ADHD and bipolar disorder via verbal fluency tasks

Abstract

BackgroundAdults with Attention Deficit Hyperactivity Disorder (ADHD) often report mental restlessness akin to racing thoughts found in hypomanic and mixed episodes of bipolar disorder (BD). Past research has suggested that racing thoughts in BD can be tackled via process-oriented verbal fluency measures. In ADHD, it is still unknown whether racing thoughts is due to comorbid BD, and its neuropsychological underpinnings remain to be investigated. To this aim, this study investigates process-oriented verbal fluency measures in adults with ADHD compared to adults with BD in a hypomanic episode, adults with ADHD + BD and healthy controls. MethodsThree verbal fluency tasks, i.e., the free, the letter and the semantic conditions, were administered to 37 adults with ADHD, 25 adults with BD in a hypomanic episode, 22 adults with comorbid ADHD + BD (euthymia) and 31 healthy subjects. Word production, clustering, and switching were analysed in verbal fluency tasks. ResultsAdults with ADHD, ADHD + BD and hypomania showed increased switches in the free verbal fluency task, compared to healthy controls, despite equivalent number of words produced. Unlike the ADHD and ADHD + BD groups, phonological clustering measures in the semantic task were increased in the hypomanic group compared to healthy controls. LimitationsBD groups were under medication. ConclusionsSemantic overactivation, reflected by increased switches in the unconstrained verbal fluency task, appear to be a common mechanism involved in racing thoughts in both ADHD and BD. By contrast, unusual sounds-based associations are specific of hypomanic speech and might contribute to the distinction trait and state racing thoughts.