The Xanax becomes a catch-22. Not for people like yourself who only take it for anxiety attacks and occasionally but if it is taken on a regular basis, it relaxes that muscles, which feels good, but the muscles need to be tight to a certain degree to keep the back in shape. The only support that the back has is the abs.
Look at older alcoholics, it is not that the beer is really putting the gut on, per se, it is that the alcohol relaxes the stomach musles and gives them a gut. I think that as time goes by, with all of the new drugs such as Xanax and Valium (relatively new in comparison to the old days of laudlum), we are going to see more back problems caused by these anti-anxiety/muscle relaxers.
How do you react to meds? Does your body metabolize them too quickly or do you have a pardoxical reaction to them?