For me personally, I think of a yoga mat. It is intended “for maintaining or encouraging a general state of health or a healthy activity”. It is intended for only general wellness and is low risk. A yoga matt would fall into category (1). It is not intended for a specific disease but can be used for lower back pain, mental therapy through meditation, or many other conditions. I personally have used it for lower back pain and can say that it works much better than a chiropractor. It also provides a place to relax after a long day, relieving stress that is associated with a number of chronic conditions and diseases.