TPH1 and irritable bowel syndrome: A previous study reported that Caucasian female patients with IBS and the TPH1 rs211105 T/G genotype showed more severe abdominal symptoms than patients with the T/T genotype.(20) Conversely, even among Caucasian patients with IBS, Jun et al.(30) detected an association between the TPH1 rs211105 T/T genotype and impairment of IBS-related cognition, which affects IBS symptoms.