Green’s Dictionary of Slang

1. amazing, fantastic, remarkable, orig. in the context of hallucinogenic drug use.

1966		New Scientist 21 Apr. 151: Already ‘mind-bending’ gases for military purposes are said to be at an advanced stage of development.
1968		L. Wolf Voices from the Love Generation 260: Maybe STP gonna be harder. It’s going to be the mind-cracking motherfucking drugs that gonna be the hard kicks.
1971		M. Novotny Kings Road 158: He’d been given a mind-bending drug.
1991		O.D. Brooks Legs 41: He’s mind-guzzling and half pissed already.
1999		Guardian Rev. 23 July 22: A mind-bending weekend of physical and psychological punishment.
2002		J. Cervantes Indoor Marijuana Horticulture xv: Cannabinoids are ingredients unique to cannabis; the psychoactive cannabinoids are responsible for the mind-bending effects of marijuana.
2015		‘Elvis Costello’ Unfaithful Music 220: I took the precaution of drinking a mind-bending amount of Pernod.

2. also in non-drug use.

1970		Sun. Times 25 Jan. 29: The theoretical mathematics of the situation are positively mind-bending.
1976		(con. 1969) C.R. Anderson Grunts 87: Living the agony of thirst and heatstroke, then gorging themselves on a sudden flood of water [...] produced a mind-bending bewilderment.
1984		C. White Life and Times of Little Richard 190: After reducing them to a frenzy with his mind-crunching Rock’n’Roll?
1985		(con. 1968) D.A. Dye Citadel (1989) 283: Get right into this mind-bending shit-storm with both feet.
2004		T. Gold Tao of Mom v: Entire libraries of huge books examine this quest in mind-bending detail.
2010		K. Richards Life 287: Waking up grateful that during the night there wasn’t a knock on the door. What a mind-bending distraction.