AIMS: The primary aim of this study was to compare plasma melatonin levels, chronotypes, sleep disturbances, and symptoms of anxiety and depression between adolescents diagnosed with Attention-Deficit/Hyperactivity Disorder (ADHD) and a healthy control group. The secondary objective was to investigate the correlation between melatonin levels and these clinical parameters within the ADHD group.
MATERIALS AND METHODS: The study sample included 41 adolescents (aged 10-18 years) who were either treatment-naïve or had not received pharmacological treatment for ADHD in the past six months. A control group of 42 age- and sex-matched healthy adolescents was included. Psychiatric assessments were conducted using the Schedule for Affective Disorders and Schizophrenia for School-Age Children. Participants completed the Revised Child Anxiety and Depression Scale (RCADS), while parents completed the Conners' Parent Rating Scale-Short Form (CPRS), the Swanson, Nolan, and Pelham Questionnaire (SNAP-IV), the Children's Chronotype Questionnaire (CCTQ), and the Sleep Disturbance Scale for Children (SDSC). Venous blood samples were collected strictly following an 8-12 h fast. Melatonin levels were measured using a competitive ELISA method.
RESULTS: Adolescents with ADHD exhibited a significantly higher prevalence of the evening-type chronotype compared to controls. Within the ADHD group, CCTQ and SNAP-IV scores were significantly higher, and sleep onset latency was significantly prolonged on both scheduled and free days. According to SDSC scores, the ADHD group experienced significantly greater difficulty in initiating and maintaining sleep and disturbances in the sleep-wake transition. Mean morning melatonin levels did not differ significantly between the ADHD (312.44 ± 102.29 pg/mL) and control groups (319.84 ± 70.75 pg/mL). However, within the ADHD group, a significant positive correlation was identified between melatonin levels and sleep onset latency. Furthermore, ADHD patients with an evening chronotype reported more severe sleep disturbances, excessive daytime sleepiness, and higher rates of inattention with psychosomatic complaints compared to other chronotypes.
CONCLUSION: Our findings suggest that adolescents with ADHD have a marked preference for eveningness and suffer from more severe sleep disturbances than their healthy peers. Although morning blood melatonin levels did not differ between groups, the positive correlation between melatonin and sleep onset latency indicates that circadian dysregulation may play a role in ADHD-related sleep pathology. However, considering the study's limitations, these results should be interpreted with caution. Interventions targeting circadian rhythms and sleep hygiene could potentially improve daily functioning in this population.
