Limitations and strengths
ADHD
One limitation of our study is the unequal distribution of female (72.5%) and male (27.5%) participants. More than half of the patients referred for the neuropsychiatric examination were females. However, there were no differences in gender distribution between adults receiving placebo first or receiving placebo at the second session. In addition, our results showed no differences in performance between females and males during the trial days. Similar proportion in gender (78% females) was reported in a Swedish study [Despite these limitations, strengths of this study are the use of data from a clinical setting. All participants had gone through careful diagnostic procedures, based on validated clinical instruments, including cognitive testing, assigned by trained clinical professionals. Retrospective reports of childhood symptoms were also obtained from the participants´ parents or other relatives. The participants had no history of previous pharmacological treatment regarding their ADHD diagnosis. During the neuropsychiatric assessment period and when the adults were in the research project, they were monitored for alcohol and drug use and females were screened for pregnancy. Before every QbTest, nicotine, snuff and caffeine use were controlled for.A crossover design was used, where participants were exposed to both test conditions similarly. We used two baselines, one for each day of the trial, to ensure current baseline values and accurately measure the difference between baselines and pills. The two baselines were also used to control for any learning effects, since earlier studies have reported better performance during the second administered CPT [Two studies have found better improvements in participants with most severe baseline symptoms, compared to participants with less severe symptoms [