1. Randomized placebo-controlled trials comparing peppermint oil and placebo for irritable bowel syndrome with a minimum treatment duration of 2 weeks.|
2. Adult patients with irritable bowel syndrome as diagnosed using any of the following criteria for IBS: Manning, Rome I, II, III, IV diagnostic criteria.
1. Non-randomized trials; observational studies such as cohort study, cross-sectional study, etc..|
2. Patients having organic disease or or did not have organic disease excluded.
3. Treatment duration of less than 2 weeks.
4. Studies with inadequate data.