Attention Deficit/Hyperactivity Disorder (ADHD) is one of the most prevalent psychiatric disorders in children (5.29%) worldwide, and highly comorbid with other psychiatric disorders.

To evaluate ADHD symptoms prevalence/frequency in young ambulatory patients diagnosed with other psychiatric disorders.

Non-interventional, multicentre, and cross-sectional, retrospective study. Patients aged 15-24 having a primary diagnosis of: Substance Use (SUD), Borderline personality (BPD), Anxiety (AD), Affective, Antisocial Personality (APD), or Conduct Disorders(CD) or Bulimia, giving inform consent were included (not previously treated/diagnosed with ADHD). ADHD symptoms prevalence was captured following DSM-IV criteria and moderate ADHD symptoms was considered as scoring >24 in the ADHD RS (DuPaul).

795 patients meeting in- and exclusion criteria were analyzed in the study. Mean age was 21.12 (SD: 2.64), and the majority were men (57.5%).A probable ADHD diagnosis (6 or more DSMIV symptoms and ADHD RS moderate symptoms) was apparent in: 40.3% of SUD patients, 23.7% of AD, 21.7% of Affective Disorders, 30.3% of Bulimia, 48.3% of BPD, 41.7% of CD and 57.1% of APD. Moreover, patients with SUD (ODD: 1.54) and BPD (ODD: 2.2) had significantly more risk vs. rest of population studied of having moderate ADHD symptoms. Also, patients having a probable ADHD diagnosis were significantly rated more severe in the GCI-Severity scale than the rest of population studied.

This cross-sectional study showed that ADHD symptoms are highly prevalent in young ambulatory patients diagnosed primarily with other psychiatric disorders, what seems to worse patient outcome if not diagnosed/managed on time. ADHD comorbidity risk varied significantly depending on the primary diagnosis.