this was changed to adhd in the dsm-iii-r, and in 1994 the dsm-iv in split the diagnosis into three subtypes: adhd inattentive type, adhd hyperactive-impulsive type, and adhd combined type. these terms were kept in the dsm-5 in 2013 and in the dsm-5-tr in 2022. prior to the dsm, terms included minimal brain damage in the 1930s. in 1934, benzedrine became the first amphetamine medication approved for use in the united states. methylphenidate was introduced in the 1950s, and enantiopure dextroamphetamine in the 1970s. the use of stimulants to treat adhd was first described in 1937. charles bradley gave the children with behavioural disorders benzedrine and found it improved academic performance and behaviour. once neuroimaging studies were possible, studies conducted in the 1990s provided support for the pre-existing theory that neurological differences - particularly in the frontal lobes - were involved in adhd. during this same period, a genetic component was identified and adhd was acknowledged to be a persistent, long-term disorder which lasted from childhood into adulthood. adhd was split into the current three sub-types because of a field trial completed by lahey and colleagues. controversy main article: attention deficit hyperactivity disorder controversies adhd, its diagnosis, and its treatment have been controversial since the 1970s. the controversies involve clinicians, teachers, policymakers, parents, and the media. positions range from the view that adhd is within the normal range of behaviour to the hypothesis that adhd is a genetic condition. other areas of controversy include the use of stimulant medications in children, the method of diagnosis, and the possibility of overdiagnosis. in 2009, the national institute for health and care excellence, while acknowledging the controversy, states that the current treatments and methods of diagnosis are based on the dominant view of the academic literature. in 2014, keith conners, one of the early advocates for recognition of the disorder, spoke out against overdiagnosis in a new york times article. in contrast, a 2014 peer-reviewed medical literature review indicated that adhd is underdiagnosed in adults. with widely differing rates of diagnosis across countries, states within countries, races, and ethnicities, some suspect factors other than the presence of the symptoms of adhd are playing a role in diagnosis, such as cultural norms. some sociologists consider adhd to be an example of the medicalization of deviant behaviour, that is, the turning of the previously non-medical issue of school performance into a medical one. most healthcare providers accept adhd as a genuine disorder, at least in the small number of people with severe symptoms. among healthcare providers the debate mainly centers on diagnosis and treatment in the much greater number of people with mild symptoms. the nature and range of desirable endpoints of adhd treatment vary among diagnostic standards for adhd. in most studies, the efficacy of treatment is determined by reductions in adhd symptoms. however, some studies have included subjective ratings from teachers and parents as part of their assessment of adhd treatment efficacies. by contrast, the subjective ratings of children undergoing adhd treatment are seldom included in studies evaluating the efficacy of adhd treatments. there have been notable differences in the diagnosis patterns of birthdays in school-age children. those born relatively younger to the school starting age than others in a classroom environment are shown to be more likely diagnosed with adhd. boys who were born in december in which the school age cut-off was december 31 were shown to be 30% more likely to be diagnosed and 41% to be treated than others born in january. girls born in december had a diagnosis percentage of 70% and 77% treatment more than ones born the following month. children who were born at the last 3 days of a calendar year were reported to have significantly higher levels of diagnosis and treatment for adhd than children born at the first 3 days of a calendar year. the studies suggest that adhd diagnosis is prone to subjective analysis. research directions possible positive traits possible positive traits of adhd are a new avenue of research, and therefore limited. a 2020 review found that creativity may be associated with adhd symptoms, particularly divergent thinking and quantity of creative achievements, but not with the disorder of adhd itself – i.e. it has not been found to be increased in people diagnosed with the disorder, only in people with subclinical symptoms or those that possess traits associated with the disorder. divergent thinking is the ability to produce creative solutions which differ significantly from each other and consider the issue from multiple perspectives. those with adhd symptoms could be advantaged in this form of creativity as they tend to have diffuse attention, allowing rapid switching between aspects of the task under consideration; flexible associative memory, allowing them to remember and use more distantly-related ideas which is associated with creativity; and impulsivity, which causes people with adhd symptoms to consider ideas which others may not have. however, people with adhd may struggle with convergent thinking, which is a cognitive process through which a set of obviously relevant knowledge is utilised in a focused effort to arrive at a single perceived best solution to a problem. a 2020 article suggested that historical documentation supported leonardo da vinci's difficulties with procrastination and time management as characteristic of adhd and that he was constantly on the go, but often jumping from task to task. possible biomarkers for diagnosis reviews of adhd biomarkers have noted that platelet monoamine oxidase expression, urinary norepinephrine, urinary mhpg, and urinary phenethylamine levels consistently differ between adhd individuals and non-adhd controls. these measurements could potentially serve as diagnostic biomarkers for adhd, but more research is needed to establish their diagnostic utility. urinary and blood plasma phenethylamine concentrations are lower in adhd individuals relative to controls and the two most commonly prescribed drugs for adhd, amphetamine and methylphenidate, increase phenethylamine biosynthesis in treatment-responsive individuals with adhd. lower urinary phenethylamine concentrations are also associated with symptoms of inattentiveness in adhd individuals.