Earlier this month a The World Federation of ADHD published an “International Consensus Statement: 208 Evidence-based Conclusions about the Disorder” to answer the many questions and claims that often surround ADHD.

In short what do we know about ADHD?

• ADHD occurs in 5.9% of youth and 2.5% of adults.
• Most cases of ADHD are caused by the combined effects of many genetic and environmental risks.
• There are small differences in the brain between people with and without ADHD.
• Untreated ADHD can lead to many adverse outcomes.
• ADHD costs society hundreds of billions of dollars each year, worldwide.

The statement is full of interesting insights such as:

• ADHD impairs the functioning of highly intelligent people, so the disorder can be diagnosed in this group. A population-based birth cohort study of over 5,700 children found no significant differences among children with high, average, or low IQ and ADHD in median age at which ADHD criteria were met, rates of learning disorders, psychiatric disorders, and substance abuse, and rates of stimulant treatment
• A meta-analysis comprising 25 studies with over eight million participants found that children and adolescents who are relatively younger than their classmates are more likely to have been diagnosed with ADHD
• Family, twin, and DNA studies show that genetic and environmental influences are partially shared between ADHD and many other psychiatric disorders (e.g. schizophrenia, depression, bipolar disorder, autism spectrum disorder, conduct disorder, eating disorders, and substance use disorders) and with somatic disorders

Do read the full accessible overview!

Much more can be read in the article/Consensus Statement from which this is the abstract:

Background: Misconceptions about ADHD stigmatize affected people, reduce credibility of providers, and prevent/delay treatment. To challenge misconceptions, we curated findings with strong evidence base.
Methods: We reviewed studies with more than 2,000 participants or meta-analyses from five or more studies or 2,000 or more participants. We excluded meta-analyses that did not assess publication bias, except for meta-analyses of prevalence. For network meta-analyses we required comparison adjusted funnel plots. We excluded treatment studies with waiting-list or treatment as usual controls. From this literature, we extracted evidence-based assertions about the disorder.
Results: We generated 208 empirically supported statements about ADHD. The status of the included statements as empirically supported is approved by 79 authors from 27 countries and 6 continents. The contents of the manuscript are endorsed by 362 people who have read this document and agree with its contents.
Conclusions: Many findings in ADHD are supported by meta-analysis. These allow for firm statements about the nature, course, outcome causes, and treatments for disorders that are useful for reducing misconceptions and stigma