LAUSR

Abstract In the present study, we propose a review and a synthesis of the work of our group about the phenomenology and the cognitive mechanisms of racing thoughts in bipolar disorder (BD) and ADHD. Contrary to the mainstream idea according to which racing thoughts are pathognomonic of BD, our work suggests that racing thoughts are enhanced in ADHD compared to hypomanic episodes of BD, whereas in euthymic episodes of BD self-reported racing thoughts are similar to the rates reported by healthy controls. Using verbal fluency tasks, we found many similarities between bipolar and ADHD subjects with one clear difference: lexical search strategy in hypomania is based on phonemic similarities rather than semantic-relatedness. However, this distinction observed in this cognitive task is certainly difficult to grasp during a clinical interview aiming to differentiate mild hypomania from combined ADHD presentation. The main landmark to distinguish them remains the episodic nature of bipolar disorders as opposed to the lifelong presentation of ADHD symptoms, a dichotomous view that is not so clear-cut in clinical practice.