I think I may understand mental illness better than I did. We humans think of ourselves as rational thinking beings, but I suspect we are just as instinctual as any other intelligent animal. We have obvious infant instincts such as suckling, imitating caregivers (especially in vocalization), and crying when something unpleasant happens. I also think we have other instincts that we excuse by rational thought or social convention. I think there is an underlying avoidance of contamination instinct. It is at its most basic about the smells of excrement and rot, but as with the sexual instinct it is modified, moderated, and reinforced by our experience or knowledge.
A perfect example of this is how people often cannot stand the food they had at the onset of some sort of illness for some time afterward. I had an awful experience of throwing up due to dizziness after having a chocolate shake and for some time following that I could not stand them. Likewise I once had pizza just before throwing up due to a gross scene in the movie
Stand By Me. For some months I did not relish pizza and I always thought I detected a underlying unpleasant smell in the odor.
I suspect that if I had allowed these initial instinctual associations to be strengthened I might have ended up avoiding a whole variety of foods. I could have ended up hating anything that had the particular aroma of tomato sauce, for example, since that was a large part of what I was reacting too. The thought of the unpleasant experience could have become linked with the instinctual impulse to avoid consuming certain things.
I further think it is at the root of many other strong reactions to food that are excused with logical or theological explanations. Like the sometimes religious rejection of meat and animal products by vegans or vegetarians. Taboos against the eating of a great variety of animals from arthropods to cattle. Perhaps even the way that some people take to the diets that reject the eating of fats or carbohydrates. Perhaps even full blown eating disorders such as anorexia could be likewise to some extent be a out of control anti-contamination instinct.
This isn't to say it is all bad. Indeed the instinctive reaction against food that is perceived to be contaminated keeps us safer from infection than if we had to weigh rationally the possibility of infection vs. the loss of food each time. Far better to play it safe and reject something emotionally rather than to take an unnecessary risk. It is just that sometimes the reaction can be too strong and overwhelm our normal day to day life. If it isn't a problem, of course, then it is just a difference. Vegetarians get along very well in our modern world with all the available food choices, though it does sometimes limit their social choices at times (the biggest advantage of being an omnivore in modern life is being able to socialize with anyone over a meal without restriction).
But it is something that a lot of us should be aware of in evaluating most mental illnesses. How many of them are normal, helpful instincts that have just gotten out of control? Become associated with too many things or are too strong? Perhaps this is the underlying problem with our ideas about depression as well. It may have logical explainable beginnings, but then it becomes part of a irrational reaction and so cannot be overcome with just someone pointing out how silly it is. A person needs either a chemical or event that "pushes reset" or else a long and drawn out effort to overcome basic instinct.
