Here's a double blind, placebo controlled study published in a rather well respected medical journal (NEJM). It shows no benefit to chronic antibiotic treatments.

<link>

Of note: I'm currently working with two pediatric infectious disease specialists in Massachusetts, both who have seen a LOT of Lyme disease (we treated 2 cases of Lyme arthritis and one case of Lyme meningitis in the last week alone), and both agree that treating "chronic lyme" with long-term antibiotics is, at this stage, ridiculous. Studies like the one above have shown no benefit to it, and long term antibiotic treatment carries risks to the person (C difficile, allergy, etc), as well as to the community (increasing community resistance).