According to Tatame.com:
The new battle between the champions of the WEC to 83kg, the Brazilian Paulão Son, and American Chael Sonnen was postponed. The fight, which was scheduled for March 26, in Las Vegas, was moved to June. "I was not in a good time, I had problems with depression, I am raising now, and the Americans were forcing me to fight now. I was not motivated to train, not training right, then decided comply with the contract and the fight was moved to June, "revealed Paulo.