Not off the top of my head, but I did a google search for:

study neck traction thoracic outlet syndrome

The first hit contained the preview text "Ineffective therapies include shoulder shrugs (useful for prevention), weight lifting, and neck traction." which is strange because it contradicts the study I read, as well as another one that said that shoulder shrugs were useful.

However, when I click through to the page which is at http://emedicine.medscape.com/article/96412-treatment , that text is gone. Maybe they corrected it?

Anyway, the 2nd hit was the one that I had read:
http://pt.unlv.edu/ebpt/cats/Orthope...ting%20TOS.pdf

I also suspect that whether or not it helps will depend on what condition your c-spine is in and probably your age as well. An older person is more likely to have spinal compression than a younger person. I'm somewhere in between in my late 30's.

I'm still using both an inversion board and neck traction, averaging every other day. It's been distinctly helpful to me; I'm a fan. ymmv