Herbert Benson, a Harvard-trained cardiologist, whose research showing the power of mind over body helped move meditation into the mainstream, died on Feb. 2 at a hospital in Boston. He was 86.

Dr. Benson was open to the possibility that state of mind could affect a person’s health — common sense today, but a radical even heretical idea when he began researching it in the mid-1960s. He wrote 11 books, several of which delved further into the physiological effects of spirituality and faith. He was the first Western doctor allowed to interview Tibetan monks about their practices, and he became friends with the Dalai Lama during that Buddhist spiritual leader’s visit to Boston in 1979.

Dr. Benson believed that praying could help a sick person, although meditation and prayer could never replace drugs and surgery completely, he said. Both medical treatment and spiritual care were necessary, he said — a fact that Western medicine had long tried to ignore, and one that he spent his career trying to correct.