The Good Vibrations hitmaker underwent two courses of treatment with Landy in the 1970s and '80s at the behest of his famous family in a desperate bid to end his life as a recluse.
Landy eventually pulled Wilson out of the mire but their relationship later soured and Landy lost his professional licence following accusations he drugged and brainwashed the star.
Despite the extreme methods of therapy Landy used to bring Wilson back from the brink of destruction, the rocker still feels thankful to the psychologist for helping to turn his life around.
Wilson tells Britain's Daily Mirror newspaper, "Yes it was a dark time in my life but I am grateful to him... He was a very forceful person but a great leader.
"He medicated me with good medication and turned me onto diet and exercise, swimming and running... I weighed 22 stone because I was just eating steaks, cake and ice-cream and he brought me down to 13.5 stone by changing my diet... I still do a lot of walking. About a mile a day. I was taught by Dr. Landy that your health is first."
Landy died in 2006. He is portrayed by Paul Giamatti in the upcoming Wilson biopic Love & Mercy.
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