how does them eating them during the rainy season help towards the idea that they eat them for the purpose of getting rid of the parasite? We arent told that the parasite is more prevelant during the rainy season or anything.

Confused because doesnt it literally say that patients who had the tendency to laugh an laughed less had more of an increase than those who dont have the tendency but laugh more? It specifically says this. So how does it overlook that possibility when it explicitly says that that isnt the case