Occupational and environmental factors cause the seasonal variation of peptic ulcers by Superposition Mechanism.

The seasonal variation of peptic ulcers, a rhythmic phenomenon with diverse patterns and controversies, has remained an unresolved mystery for more than 90 years. A recent study identified that environmental factors cause peptic ulcers by inducing psychological stress. Based on this etiology, a synthetic review found that seasonal changes profoundly affect multiple occupational and environmental factors, each of which plays a causal role in peptic ulcers if they are studied individually. An integration of the monthly incidences caused by three occupational and environmental factors simulated the fluctuation curves in three representative seasonal patterns. The similarity between the simulated and original curves suggests that multiple occupational and environmental factors cause the seasonal variation by Superposition Mechanism, and regional differences in occupational and environmental factors account for the diverse patterns and controversies. Significantly, a full understanding of the seasonal variation of peptic ulcers validated a new concept, Superposition Mechanism, which may represent an indispensable methodological complement to modern life science and medicine.