^aDivision of Pain Medicine, Massachusetts General Hospital Pain Center, Boston, MA 02114, USA

^bHarvard Medical School, Boston Massachusetts, USA

^cFinnish Genome Center, The University of Helsinki, Helsinki, Finland

^*Corresponding author. Address: Division of Pain Medicine, Massachusetts General Hospital Pain Center, 15 Parkman Street, WACC 333 Boston, MA 02114, USA. Tel.: +1 617 724 2113; fax: +1 617 724 2719.

E-mail: [email protected]

Submitted June 26, 2006; received in revised form February 22, 2007; accepted March 23, 2007.