Figure 3 shows a flow diagram of studies and the final subset for review of KQ3. A separate search was performed for prevalence reports (KQ3). The initial yield of papers was 8,502 of which 5,964 were excluded at the title and abstract screening level 1, with an additional 1,918 excluded at level 2. Of the remaining 620 papers, an additional 132 were excluded at full text screening. Having applied the methodology of systematic review to reduce the volume of papers, the authors then addressed KQ3 using data from 94 of the 485 reports selected as a result of a scan of abstracts and then augmented with other supporting methodological and epidemiological studies which informed discussion of issues surrounding estimates of prevalence.

Figure 3KQ 3. Flow of studies through review for prevalence question

From: Results

Cover of Attention Deficit Hyperactivity Disorder
Attention Deficit Hyperactivity Disorder: Effectiveness of Treatment in At-Risk Preschoolers; Long-Term Effectiveness in All Ages; and Variability in Prevalence, Diagnosis, and Treatment [Internet].
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Charach A, Dashti B, Carson P, et al.

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