With regard to your question concerning spiritual healing: Such a healing constitutes, indeed, one of the most effective methods of relieving a person from either his mental or physical pains and sufferings. 'Abdu'l-Bahá has in His "Paris Talks" emphasized its importance by stating that it should be used as an essential means for effecting a complete physical cure. Spiritual healing, however, is not and cannot be a substitute for material healing, but it is a most valuable adjunct to it. Both are, indeed, essential and complementary.
(From a letter dated 16 February 1935 written on behalf of Shoghi Effendi to an individual believer; The Compilation of Compilations, vol. I, Health, Healing and Nutrition)