Please have a read of the discussion here: Are magic tricks in scope?
Please also have a read of the answer of the duplicated question that directly addresses your question, particularly the quote from Derren Brown:
I am often dishonest in my techniques, but always honest about my dishonesty. As I say in each show, 'I mix magic, suggestion, psychology, misdirection and showmanship'. I happily admit cheating, as it's all part of the game. I hope some of the fun for the viewer comes from not knowing what's real and what isn't. I am an entertainer first and foremost, and I am careful not to cross any moral line that would take me into manipulating people's real-life decisions or belief systems.
It isn't necessary to investigate whether subliminal messages work the way Derren Brown represents them, because it is not a notable claim. because Derren Brown is a professional magician who proudly tells falsehoods for a living.