I recently came across a whole range of papers about Tai Chi for health in The American Journal of Physical Medicine & Rehabilitation – all positive stuff and worth a read.
Subjects include :
Tai Chi for Stroke Rehabilitation
Tai Chi Treatment for Depression in Chinese Americans
Evaluating the Safety and Potential Use of A Weight-Bearing Exercise, Tai-Chi Chuan, for Rheumatoid Arthritis Patients
Comprehensive Therapeutic Benefits of Taiji: A Critical Review
Also from Natural News a couple of pieces on Parkinsons:
http://www.naturalnews.com/037448_Parkinsons_disease_nutritional_therapy_Tai_Chi.html
http://www.naturalnews.com/034971_Tai_Chi_Parkinsons_arthritis.html
and from Hindawi publishing a piece on Tai Chi for Patients with Schizophrenia:
http://www.hindawi.com/journals/ecam/2012/923925/