Fig. 4

Flowchart depicting how studies were selected for this review: PubMed research yielded 78 studies. We used the MeSH terms “PPI use” and “microbiome”. Exclusion criteria were: Studies not performed on PPIs, studies not performed on humans and, studies that did not meet inclusion criteria, f.e. studies that were performed on the influence of PPI use on other than headache diseases (n = 27), or studies performed on the pharmacodynamics of PPIs etc.. A total of 28 studies were included, although not all were citied. The final research was done on the 8.^th of December in 2024