ADHD is the most common pediatric neurobehavioral disorder, and among adults who are seeking treatment for mental health, about 16% have ADHD. Unfortunately, only 1 in 5 adults with ADHD receive treatment due to substantial barriers to care and adequate assessment.
In 1798, Sir Alexander Crichton, a Scottish physician, made early observations about a cluster of behavioral symptoms predominantly characterized by distractibility and a significant deficit in sustained attention and concentration. He documented that these symptoms manifested early in the course of an individual's life. His observations bear a striking resemblance to what is contemporarily understood and classified as Attention-Deficit Hyperactivity Disorder (ADHD).
Moving forward to the dawn of the 20th century, Sir George Frederic Still delivered a series of lectures in 1902 wherein he elucidated specific mental conditions affecting children of normal intelligence levels. Still’s focus was on children who exhibited heightened impulsivity, deficits in attention, and challenges with self-regulation. Notably, he identified a gender-based prevalence, observing 15 cases in males as opposed to five in females, thereby foreshadowing contemporary epidemiological data that suggests a higher incidence of ADHD diagnoses among males.
In the early 1930s, German physicians Franz Kramer and Hans Pollnow introduced the term "hyperkinetic disease" to describe children who were notably restless and exhibited considerable difficulties in conforming to social norms and classroom expectations. These symptoms were noted to manifest in early childhood, typically around the ages of 3 or 4, and peak at age 6. The severity of the restlessness appeared to ameliorate by age 7, and most of the children showed improvement as they matured into adolescence and adulthood.
In a seminal moment for psychopharmacology in 1937, Charles Bradley, then the Medical Director of what is now known as Bradley Hospital in East Providence, Rhode Island, observed that Benzedrine, a stimulant, had a paradoxically calming effect on children and enhanced their academic performance. Despite FDA approval for Benzedrine in 1936, Bradley's revelations would not gain substantial research traction until years later.
The formal psychiatric recognition of this condition came in 1968 when it was included in the second edition of the American Psychiatric Association's "Diagnostic and Statistical Manual of Mental Disorders" (DSM-II) under the nomenclature "Hyperkinetic Reaction of Childhood." Subsequent to that, the DSM-III, released in 1980, revised the taxonomy to "Attention Deficit Disorder" (ADD), bifurcating it into two subtypes: ADD with hyperactivity and ADD without hyperactivity.
In a further taxonomic adjustment in 1987, the DSM-III-R amalgamated these variations under the title "Attention Deficit Hyperactivity Disorder" (ADHD), thereby acknowledging the triad of core symptoms: inattention, impulsivity, and hyperactivity, as dimensions of a singular disorder.
The fourth edition of the DSM, published in 1994, refined the diagnostic criteria and delineated three primary presentations of ADHD: Predominantly Inattentive, Predominantly Hyperactive-Impulsive, and Combined Presentation. This edition was also groundbreaking in acknowledging the chronicity of the disorder, indicating that symptoms can persist into adulthood.
In its fifth and most recent edition in 2013, the DSM-5 retained these three presentations but reclassified them as "presentations" rather than "types" to highlight the fluidity and potential evolution of symptoms across the lifespan.
Various theories propose that the origin and variability of Attention-Deficit/Hyperactivity Disorder (ADHD) are significantly influenced by deficiencies in cognitive and reward mechanisms. Among these theories are:
These theories collectively propose that ADHD is not a homogeneous condition but rather is characterized by a range of cognitive and motivational impairments. By understanding these theories, clinicians and researchers can better conceptualize ADHD and thereby develop more targeted treatment approaches.