The first international consensus statement on ADHD was published in 2002 (Barkley et al, 2002). The aim of the current edition was to update the original consensus statement by cataloguing important scientific discoveries from the last 20 years.
Evidence-based ADHD statements were identified through examination of published high quality meta-analyses and large studies. Large cohort studies* and meta-analyses† were searched for on PubMed. For inclusion, each evidence-based statement had to be supported by meta-analyses or by large registry studies with more than 2000 participants. Meta-analyses had to report data from ≥5 studies or the chosen studies must have had a cumulative total of 2000 participants. Statements about the history of ADHD and its diagnostic criteria did not require support from meta-analyses or large registry studies.
In total, 208 empirically supported statements about ADHD were generated. The statements were approved by 79 authors from 27 countries and six continents and endorsed by 362 people. Key findings from the study included:
- ADHD has been described in the medical literature since 1775.
- The diagnosis of ADHD, even in the presence of other psychiatric disorders, could be well defined and valid at all ages when made by a licensed clinician.
- ADHD is more common in males and occurs in 5.9% of youth and 2.5% of adults, and has been found in studies around the world.
- ADHD is typically caused by the combined effects of many genetic and environmental risks.
- Individuals with ADHD can show impaired performance on psychological tests of brain functioning; however, these tests cannot be used to diagnose ADHD.
- Neuroimaging studies have found small differences between individuals with and without ADHD in the structure and functioning of the brain. These differences cannot be used to diagnose ADHD.
- Individuals with ADHD are at increased risk for various comorbidities such as allergies, asthma, diabetes mellitus, epilepsy, eye abnormalities, hypertension, immune disorders, metabolic disorders, obesity, psoriasis, sexually transmitted infections and sleep problems.
- Individuals with ADHD are at increased risk for accidental injuries, delinquency, difficulties socialising, educational underachievement, gambling, low quality of life, premature death, social challenges, substance-use disorders, suicide, teenage pregnancy and unemployment.
- Economic burden studies show that ADHD costs society billions of dollars each year around the world.
- Regulatory agencies have determined that several medications can reduce the symptoms of ADHD through randomised controlled clinical trial data.
- Treatment with ADHD medication has been shown to reduce accidental injuries, depression and educational underachievement.
- The adverse effects of medications for ADHD may be mild, and in some instances can be addressed by altering dose or medication.
- It has been reported that stimulant medications for ADHD may be more effective than non-stimulant medications; however, in some instances, they are more likely to be diverted, misused or abused.
- Non-medication treatments for ADHD are frequently useful to help problems that remain after medication has been optimised.
A limitation of this consensus statement was that well-established research findings for which meta-analyses or very large studies do not exist were not reported.
The authors concluded that many key findings in ADHD are supported by meta-analyses, which enable the generation of statements about ADHD and its treatment that may be useful for reducing misconceptions and stigma.
Read more about the 2021 ADHD international consensus statements here
*PubMed search strategy for large cohort studies included: ADHD [Title/Abstract] AND (nationwide [Title/Abstract] OR national [Title/Abstract] OR register [Title/Abstract] OR registry [Title/Abstract]) NOT review [Publication Type] NOT meta-analysis [Publication Type]
†PubMed search strategy for meta-analyses included: ADHD [All Fields] AND (meta-analysis [Title] OR meta-analysis [Title] OR meta-analytic [Title] OR systematic review [Title])
Barkley RA. International consensus statement on ADHD. Clin Child Fam Psychol Rev 2002; 5: 89-111.
Faraone SV, Banaschewski T, Coghill D, et al. The World Federation of ADHD international consensus statement: 208 evidence-based conclusions about the disorder. Neurosci Biobehav Rev 2021; Epub ahead of print.