ADHD symptoms in adults with delayed sleep phase disorder

The aims of the study are to investigate the prevalence of ADHD in delayed sleep phase disorder (DSPD) patients and to explore the relationship between circadian phase and ADHD symptoms, using the dim light melatonin onset (DLMO), and to compare this relationship with patients with sleep problems other than DSPD. 353 adult patients with sleep problems were assessed for self-reported ADHD symptoms using ADHD rating scale, self-reported sleep disorders using Holland Sleep Disorders Questionnaire (HSDQ), and circadian rhythmicity using salivary DLMO. From the 353 patients with sleep problems, 63 were designated as DSPD and 107 (30.3%) reported probable ADHD. Probable ADHD was reported by 47.6% of the DSPD patients and by 26.9% of the non-DSPD patients (p = 0.059). The DSPD group showed significant higher total ADHD-RS scores (p = 0.011). In the probable ADHD group more patients were designated as DSPD (28%) compared to the non-ADHD group (13.6% [χ2 = 10.402, p = 0.001]). Also 20 min later, DLMO (22:46 h) was found (p = 0.017) and more positive HSDQ scores on insomnia, parasomnia, hypersomnia, and sleep-related breathing disorders were reported in the probable ADHD group than in the non-probable ADHD group (χ2 resp. 16.07; p < 0.001, 9.245; p = 0.002, 19.391; p < 0.00 and 5.865; p = 0.059). The data suggest a high prevalence of probable ADHD in DSPD patients and increased prevalence of DSPD and other sleep disorders in patients with probable ADHD. Consequence is that awareness of these findings might help with treatment of both DSPD and ADHD.