IntroductionChronic Fatigue Syndrome (CFS) is characterized by severe fatigue associated with pain, sleep disturbance, attentional impairment and headaches. Evidence points towards a prominent role for Central Nervous System in its pathogenesis, and alterations in serotoninergic and dopaminergic neurotransmission have been described.Attention-deficit Hyperactivity Disorder (ADHD) courses with inattention, impulsivity, and hyperactivity. It affects children and persists into adulthood in 50% of patients. Dopamine transporter abnormalities lead to impaired neurotransmission of catecholaminergic frontal-subcortical-cerebellar circuits.ObjectivesTo describe the prevalence of ADHD in a sample of CFS patients, and the clinical implications of the association.AimsTo study the relationship between CFS and ADHD.MethodsThe initial sample consisted of 142 patients, of whom 9 were excluded because of severe psychopathology or incomplete evaluation. All the patients (age 49 ± 87; 94,7 women) received CFS diagnoses according to Fukuda criteria. ADHD was assessed with a diagnostic interview (CAADID), ADHD Rating Scale and the scale WURS, for childhood diagnose. The scales FIS-40, HAD, STAI and Pluthik Risk of Suicide (RS) were administrated.Results38 patients (28,8%) were diagnosed of childhood ADHD (4 combined, 22 hyperactive-impulsive, 12 inattentive) and persisted into adulthood in 28 (21,1%; 5 combined, 4 hyperactive-impulsive, 19 inattentive). There were no differences in Fukuda criteria profile and FIS-40 between groups. ADHD patients scored higher in HAD-Anxiety (9,88 ± 4,82 vs. 12,57 ± 3,49; p = 0,007), HAD-Depression (9,69 ± 4,84 vs. 12,04 ± 4,53; p = 0,023), STAI-E (30,55 ± 14,53 vs. 38,41 ± 11,35; p = 0,012), and RS (6,13 ± 3,48 vs. 8,49 ± 3,07; p = 0,002).ConclusionsADHD is frequent in CFS patients and it is associated with more severe clinical profile.