The International Collaboration on ADHD and Substance Abuse (ICASA): Mission, Results, and Future Activities

Eur Addict Res. 2020;26(4-5):173-178. doi: 10.1159/000508870. Epub 2020 Jun 29.


Background: The International Collaboration on ADHD and Substance Abuse (ICASA) is a network of 28 centers from 16 countries initiated to investigate the link between attention deficit-hyperactivity disorder (ADHD) and substance use disorder (SUD). In this article, we present the mission, the results of finished studies, and the current and future research projects of ICASA.

Methods: During the past 10 years, 3 cross-sectional studies were conducted: two International ADHD in Substance use disorders Prevalence (IASP-1 and IASP-2) studies, directed at the screening, diagnosis, and the prevalence of adult ADHD in treatment-seeking patients with SUD, and the Continuous performance test for ADHD in SUD Patients (CASP) study, testing a novel continuous performance test in SUD patients with and without adult ADHD. Recently, the prospective International Naturalistic Cohort Study of ADHD and Substance Use Disorders (INCAS) was initiated, directed at treatment provision and treatment outcome in SUD patients with adult ADHD.

Results: The IASP studies have shown that approximately 1 in 6 adult treatment-seeking SUD patients also have ADHD. In addition, those SUD patients with adult ADHD compared to SUD patients without ADHD report more childhood trauma exposure, slower infant development, greater problems controlling their temperament, and lower educational attainment. Comorbid patients also reported more risk-taking behavior, and a higher rate of other psychiatric disorders compared to SUD patients without ADHD. Screening, diagnosis, and treatment of this patient group are possible even before abstinence has been achieved. The results of the CASP study are reported separately in this special issue.

Conclusions: The ICASA research to date has demonstrated a high prevalence of comorbid ADHD and SUD, associated with elevated rates of additional comorbidities and risk factors for adverse outcomes. More research is needed to find the best way to treat these patients, which is the main topic of the ongoing INCAS study.

Keywords: Attention deficit-hyperactivity disorder; CASP study; IASP-1 study; IASP-2 study; ICASA; INCAS study; Substance use disorder.

Publication types

  • Review

MeSH terms

  • Adverse Childhood Experiences / psychology
  • Attention Deficit Disorder with Hyperactivity / diagnosis
  • Attention Deficit Disorder with Hyperactivity / epidemiology*
  • Brief Psychiatric Rating Scale
  • Comorbidity*
  • Humans
  • Internationality
  • Mass Screening
  • Prevalence
  • Risk Factors
  • Substance-Related Disorders / diagnosis
  • Substance-Related Disorders / epidemiology*
  • Substance-Related Disorders / therapy
  • Temperament