Beyond motor hyperactivity: Racing thoughts are an integral symptom of adult attention deficit hyperactivity disorder.

Adults with ADHD experience mental restlessness, akin to racing thoughts, but data on this symptom in ADHD remain scarce. Our study aims at investigating self-reported racing thoughts in adults with ADHD, and its relationship with affective dysregulation and insomnia. We were also interested in whether racing thoughts may aid differential diagnosis with bipolar disorder (BD). 182 adults with ADHD, 30 ADHD+BD, 31 hypomanic BD, and 20 euthymic BD patients completed the Racing and Crowded Thoughts Questionnaire (RCTQ). ADHD, anxiety, insomnia and depression symptoms, as well as affective temperament were also assessed in ADHD and ADHD+BD subjects. Results show that RCTQ scores were higher in ADHD compared to hypomania and euthymia and were associated with cyclothymic traits and anxiety. Moreover, in ADHD and ADHD+BD, racing thoughts increased in the evening and at bedtime and were associated with insomnia severity. In conclusion, self-reported racing thoughts are a neglected but an intrinsic feature of adult ADHD that is particularly related to cyclothymia and anxiety, but cannot differentiate ADHD and BD.