Well, if it's mental illness, nobody knows what causes it. People have theories but we don't know. Toxin overflow is a pretty vague and large category -- everyone who lives in modern society has a toxin overflow as we're exposed daily to chemicals in our water, food and air that weren't around not that long ago but that doesn't seem to give most people mental disorders; on the other hand, there is an epidemic of them and no doubt these toxins are at least partly to blame. Exposure to certain neurotoxins especially when young, such as mercury and lead, can cause mental problems but usually affect the very young more than older people. You say you eat a healthy diet, but what you think is healthy might not be, but again, most people don't eat a healthy diet but don't have mental illness. They get sick eventually but don't get anxiety or depression. There are foods that can cause this, however, such as foods you're allergic to or if you have something like Celiac disease. And then there's the thyroid, which when it goes wrong can cause what you're feeling and sometimes it goes wrong because of toxins and sometimes because of a lack of iodine or too much iodine. Insufficient Vitamin D or B vitamins or magnesium can cause what you're feeling and can arise even though you think you're eating well or taking a multivitamin, because most of them are awful and use ingredients you can't absorb, but none of them can replace a good diet. So who knows? The best you can do is get the best work-up you can get from your doctor and, if nothing is found, see a good therapist. Sometimes this stuff just arises, usually from the late teens to the late twenties, and nobody can tell you why.