"Diabetes is caused by melancholy"

This quote by Thomas Willis recommends that diabetes is triggered by a state of unhappiness or anxiety. This is an interesting idea, as it implies that a person's emotion can have an impact on their physical health. It is possible that Willis was referring to the idea that stress and depression can result in unhealthy lifestyle choices, such as overindulging and lack of workout, which can in turn lead to diabetes. It is likewise possible that Willis was describing the concept that depression can cause a weakened immune system, which can make an individual more vulnerable to diabetes. Whatever the case, this quote recommends that psychological health can have a direct impact on physical health.