Yoga is not a therapy for ailments nor confined to Ashtanga yoga and practice for an hour or so.in fact yoga is to be rehearsed for 24 hours.it is just not Milan of Atma with Paramatma as people quote Yuj means joining.yoga is practical aspect of Vedic science.
Aspects of yoga are beyond Asthanga. Yama, niyama, Asana, Pranayam, Pratyahar, Dharna, Dhyan, samadhi, Laya, bhakti, kundalini, mantra, Japa, gyan, swara, kriya, karma etc.
If one starts following these aspects, he will have to devot 24 hours a day and therefore yoga becomes a lifestyle.
For god sake do not consider yoga as therapy.it is just a by-product.