Pain genetics: past, present and future.

Chronic pain is a classic example of gene × environment interaction: inflammatory and/or nerve injuries are known or suspected to be the etiology of most chronic pain syndromes, but only a small minority of those subjected to such injuries actually develop chronic pain. Once chronic pain has developed, pain severity and analgesic response are also highly variable among individuals. Although animal genetics studies have been ongoing for over two decades, only recently have comprehensive human twin studies and large-scale association studies been performed. Here, I review recent and accelerating progress in, and continuing challenges to, the identification of genes contributing to such variability. Success in this endeavor will hopefully lead to both better management of pain using currently available therapies and the development and/or prioritizing of new ones.