Just to clarify: the equine therapy I did for several months did not involve any riding, though some people end up doing that. No leads were used either. It's more about the relationship and how the horse is so finely tuned to the person that they only feel safe when someone is being congruent (ex: they will not approach if you are being fake confident, but if you are honestly hurting and open, they will tend to you--it brings things up that are good for processing in therapy). It's too complex to describe here, but there has been a lot written about this kind of therapy, especially for children who have been abused.