Kennedy also suffered from chronic and severe back pain, for which he had surgery and was written up in the American Medical Association's "Archives of Surgery". Kennedy's condition may have had diplomatic repercussions, as he appears to have been taking a combination of drugs to treat severe back pain during the 1961 Vienna Summit with Soviet Premier Nikita Khrushchev. The combination included hormones, animal organ cells, steroids, vitamins, enzymes, and amphetamines, and possible potential side effects included hyperactivity, hypertension, impaired judgment, nervousness, and mood swings. Kennedy at one time was regularly seen by no fewer than three doctors, one of whom, Max Jacobson, was unknown to the other two, as his mode of treatment was controversial and used for the most severe bouts of back pain.