It can help you lessen back pain by making you aware of what brings it on. Yoga is an excellent therapy to relax. When your attention is directed inward, your body receives messages that you are safe and secure and that it is appropriate to relax. So muscles relax, blood pressure drops, nerves are calmed, anxiety is decreased, immunity is heightened, and healing is enhanced. All of these things can greatly improve one's ability to deal with both the symptoms and causes of back pain.
Yoga is also excellent to prevent back pain.
A qualified yoga professional can tailor a specific yoga program to your needs. When you have a backache, you should not do any yoga postures without expert guidance. This is especially true if your pain comes from a slipped disk.