There's a very recent paper on PeerJ (hooray, open access), perhaps not what one would call "scientific backing" in the strongest sense, but more a study aiming to establish the scope of the phenomenon, and relate it to other aspects of perceptual experience - through survey of self-reported ASMR experiencers: Barratt & Davis, 2015

While ASMR appears to be a genuine, relatively prevalent perceptual experience, the exact nature of the phenomenon is still unknown....

Full survey data is also provided as supplemental information (see the link above) in case anyone wants to do some deeper digging.