In general, antidepressants are considered more effective since they are a drug, as opposed to a complementary therapy. Although some studies consider that 70% of these drugs are ineffective, we use them daily and they are covered by the provincial health systems.
Doesn't that prove then that there is no way of demonstrating that complementary therapies, such as horse-assisted therapy, are useless or ineffective? This supports your argument that we cannot demonstrate that it's ineffective.