In 2004 David Shapiro, Ph.D. and Karen Cline, B.A., published a study in the International Journal of Yoga Therapy (No. 14) with two objectives. First, “examine changes in self-reported moods and emotioinal states from before and after Iyengar Yoga classes and how they are affected by the practice of different types of Yoga poses” and second, “to deternine whethere observed changes in mood depend on one’s personality traits”.
“The main objective of [this] study was to test the hypothesis derived from Iyengar Yoga teaching and theory that the practice of back bends results in increases in positive emotional states (feeling happy or elated) and decreases in negative emotional states (feeling sad or depressed).” “To control for nonspecific factors, the effects of back bends were compared with the effects of two other typical Yoga practices (forward bends and standing poses). In this way, [it] could [be] determine[d] whether the expected changes in moods would be more pronounced in or specific to the practice of back bends.”
“By comparing the effects of the different class types within the same subjects, we could determine whether changes in self-reported moods from before to after a session would vary as a function of the specific focus on a given Yoga practice.” “A second aim was to test the hypothesis that mood changes asso- ciated with the different Yoga prac- tices would be related to personality traits. For this purpose, individual differences in anxiety, depression, and hostility were examined. These traits are related to emotional behavior and experience and may predict how a person’s mood changes with the practice of the different poses.”
Conclusion
“The practice of Yoga appears to result in increases in positive moods, decreases in negative moods, and increases in energy level regardless of the âsana practiced. Despite the effort and sustained physical exertion in Yoga, psychological wellbeing is enhanced after a Yoga class, which no doubt reinforces further participation. These effects tend to last at least for a few hours after a class. The specific poses also appear to result in differences in how moods are affected, although these results need to be replicated in a larger sample. The topic of social, psychological, and physiological mechanisms of movements is worthy of further attention. Moreover, the fact that mood changes may be in part dependent on one’s characteristic coping styles deserves further investigation. Back bends appear to be effective in increasing positive moods in general and in individuals who are relatively hostile or depressed. Yoga should be investigated for its potential clinical application in mood disorders and depression and in the management of hostility.”
http://iynaus.org/sites/iynaus_files/pages/research/MoodDisordersIyengaryoga.pdf
Rafael Durán 
Another good article, thx! -Jon Sent from Yahoo il on Android