ADHD cannot be confirmed with a blood test or brain scan, but the scientific consensus supports its validity as a real disorder, writes Stephen V. Faraone, Ph.D., a distinguished professor of psychiatry at SUNY Upstate Medical University.
Critics point to the absence of a biomarker as evidence that ADHD is a social construct or a medicalization of normal childhood energy. However, many indisputably valid medical disorders lack biomarkers. Migraine headaches, trigeminal neuralgia, myalgic encephalomyelitis, complex regional pain syndrome, interstitial cystitis, and mild traumatic brain injury are all recognized physical diseases without definitive biomarker tests.
The 2021 World Federation of ADHD International Consensus Statement asserts that ADHD is a valid, highly heritable, and neurobiologically grounded disorder. ADHD meets established psychiatric criteria for what constitutes a disorder.
Inattention, impulsivity, and hyperactivity form a consistent and recognizable pattern with clear functional impairments, ranging from severe academic problems and poor peer relations to accidental injuries and occupational failure. Many studies document impaired performance on neuropsychological tests, small differences in brain structure and function, and genetic variants that increase risk for ADHD. ADHD symptoms differ from those used to diagnose commonly coexisting disorders such as anxiety and mood disorders.
ADHD has high heritability and DNA studies show that most cases result from the accumulation of many genetic risk variants. Symptoms continue from childhood to adulthood. Substantial evidence supports the benefit of stimulant and non-stimulant medications, parent behavior therapy for children, and cognitive behavioral therapy for adults.
Faraone writes that ADHD's validity is established through "an overwhelming convergence of scientific evidence: a highly reliable behavioral phenotype, strong genetic heritability, distinct population-level neurobiological correlates, severe and measurable life impairments, and a clear response to medical and psychological treatments."