Hindawi Publishing Corporation Evidence-Based Complementary and Alternative Medicine Volume 2012, Article ID 678107, 9 pages doi:10.1155/2012/678107 Review Article A Review Focused on the Psychological Effectiveness of Tai Chi on Different Populations Long Zhang,1 Charles Layne,2 Thomas Lowder,2 and Jian Liu2 1 Department Of Physical Education, Shenzhen Polytechnic, Shenzhen 518055, China 2 Department of Health And Human Performance, The University of Houston, Houston, TX 77204-6015, USA Correspondence should be addressed to Long Zhang, tuahb@hotmail.com Received 12 April 2011; Accepted 16 May 2011 Academic Editor: Ke Ren Copyright © 2012 Long Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. As a popular exercise form, Tai Chi (TC) has been investigated to determine its contributions to an active and healthy lifestyle. There are an increasing number of researchers who focus on exploring the potential physiological and psychological beneﬁts of TC but only a few systematic reviews of these beneﬁts to a variety of populations. The purpose of this paper is to comprehensively evaluate the reported psychological beneﬁts associated with practicing TC. Although many investigators have reported possible psychological beneﬁts of TC for children, young adults, older healthy adults, and for a variety of patient populations, many of the reports suﬀer one or more methodological ﬂaws. These ﬂaws include inadequate study design, including lack of control groups, small sample sizes, unsophisticated statistical techniques, or publication without rigorous peer review. After reviewing the results of the existing literature regarding the potential psychological beneﬁts of TC, we recommend that future investigations be conducted with additional adherence to the traditional scientiﬁc process. 1. Introduction Increasing amounts of scientiﬁc evidence suggest that TC is related to improvements in mental health, psychosocial well-being, stress reduction, and self-reported sleep duration [1–5]. These beneﬁts have been reported across a range of populations including children, healthy young and old adults and patient population such as those individuals with Parkinson’s, cardiovascular disease, and AIDS. Other investi- gators have cast doubt on these ﬁndings by reporting little or no psychological beneﬁts resulting from practicing TC. The objective of this paper is to summarize the existing litera- ture concerning the potential psychological beneﬁts of TC, including the physiological processes reported to be related to psychological variables, across a variety of participant groups. Additionally, recommendations are provided con- cerning the conduct of future investigations involving TC. 2. The Mechanism That Physiology Responds to Exercise to Produce Psychological Beneﬁts As a form of exercise, there is every reason to assume that the body’s physiological systems respond to TC training in the same manner these systems respond to other forms of moderately intense exercising. This assumption includes those responses that have a directly mediating eﬀect on psychological variables. Evidence that physiological factors may explain the beneﬁcial eﬀect of exercise on psychological well-being derives from research showing that exercise promotes the secretion of serotonin and dopamine, which in turn enhances aminergic synaptic transmission in the central nervous system [6]. Evidence from animal studies suggests that exercise stimulates the secretion of endogenous opioids (endorphins) and produces a state of euphoria [7]. Shyu Bai-Chuang et al. [8] also suggest that long-lasting muscle exercise (e.g., jogging) in rats produces discharges in muscle aﬀerents which inﬂuence central endorphin mechanisms giving analgetic eﬀects, and as a result mediated increase in pain threshold of the exercising rats. John Rodgers and Jill Randall (1985) report their study on “social conﬂict” analgesia in intruder mice which follows attack from aggressive residents; their investigation shows how opioid antagonists and cross-tolerance with morphine can be used to establish opioid involvement in an originally nonopioid, that is, behaviourally induced, form of analgesia. The reader is referred to Steinberg Hannan and Elizabeth Sykes [9].