Table 1 Search terms and syntax

{("Headache"[Mesh] OR "Headache Disorders"[Mesh] OR headache*[Text Word] OR migraine*[Text Word])

AND

("Cost of Illness"[Mesh] OR "Absenteeism"[Mesh] OR "Presenteeism"[Mesh] OR "Sick Leave"[Mesh] OR productivity[Text Word] OR productive time[Text Word] OR absenteeism[Text Word] OR presenteeism[Text Word] OR sick leave[Text Word] OR indirect cost[Text Word] OR MIDAS[Text Word])

AND

(disabilit*[Text Word] OR frequency[Text Word] OR duration[Text Word])

AND

English[lang]}

{NOT

("Animals"[Mesh] NOT "Humans"[Mesh])}

{NOT

("Review" [Publication Type] OR "Meta-Analysis" [Publication Type] OR "Letter" [Publication Type] OR "Congresses" [Publication Type] OR "Case Reports" [Publication Type])}