Substance use disorders (SUD) often co-occur with attention deficit hyperactivity
disorder (ADHD). Although the short-term effects of some specific interventions have
been investigated in randomized clinical trials, little is known about the long-term
clinical course of treatment-seeking SUD patients with comorbid ADHD.This paper presents
the protocol and baseline clinical characteristics of the International Naturalistic
Cohort Study of ADHD and SUD (INCAS) designed and conducted by the International Collaboration
on ADHD and Substance Abuse (ICASA) foundation. The overall aim of INCAS is to investigate
the treatment modalities provided to treatment-seeking SUD patients with comorbid
ADHD, and to describe the clinical course and identify predictors for treatment outcomes.
This ongoing study employs a multicentre observational prospective cohort design.
Treatment-seeking adult SUD patients with comorbid ADHD are recruited, at 12 study
sites in nine different countries. During the follow-up period of nine months, data
is collected through patient files, interviews, and self-rating scales, targeting
a broad range of cognitive and clinical symptom domains, at baseline, four weeks,
three months and nine months.A clinically representative sample of 578 patients (137
females, 441 males) was enrolled during the recruitment period (June 2017-May 2021).
At baseline, the sample had a mean age (SD) of 36.7 years (11.0); 47.5% were inpatients
and 52.5% outpatients; The most prevalent SUDs were with alcohol 54.2%, stimulants
43.6%, cannabis 33.1%, and opioids 14.5%. Patients reported previous treatments for
SUD in 71.1% and for ADHD in 56.9%. Other comorbid mental disorders were present in
61.4% of the sample: major depression 31.5%, post-traumatic stress disorder 12.1%,
borderline personality disorder 10.2%.The first baseline results of this international
cohort study speak to its feasibility. Data show that many SUD patients with comorbid
ADHD had never received treatment for their ADHD prior to enrolment in the study.
Future reports on this study will identify the course and potential predictors for
successful pharmaceutical and psychological treatment outcomes.ISRCTN15998989 20/12/2019.
