In 2007, O'Sullivan won his third Masters title and his fourth UK Championship, his first ranking title in almost three years. He won his third world title in 2008, defeating Ali Carter 18–8 in the final, after which he held the world number one ranking for the next two seasons. He added his fourth Masters title in 2009. After two seasons that saw him fall out of the top ten in the world rankings for the first time, he began working with psychiatrist Steve Peters in 2011. A resurgent O'Sullivan captured his fourth World Championship in 2012, again defeating Carter in the final, after which he paid tribute to Peters's work with him. The following season, he took an extended break from the professional tour. Despite playing only one competitive match all season, he returned to the Crucible for the 2013 World Snooker Championship and successfully defended his world title, defeating Barry Hawkins 18–12 in the final. In his 2014 Masters quarterfinal against Ricky Walden, he set a new record for the most points without reply in professional competition, with 556, and went on to beat the defending champion Mark Selby 10–4 in the final to claim his fifth Masters title. At the 2014 World Championship, he reached a third consecutive world final, where he again faced Selby. Despite taking a 10–5 lead, O'Sullivan lost 14–18, his first defeat in a world final. Later in 2014, he won his fifth UK Championship, beating Judd Trump 10–9 in the final, although he declined to defend his UK title the following year, citing debilitating insomnia.