Perhaps half of all patients who need post -surgical or cancer pain relief are under-medicated, according to studies cited by Dr. Eric Grigsby, director of the Pain Service at thhe UC Davis Medical Center. Grigsby says that some 15 studies conducted during the past 18 years reveal that "anywhere from 40 to 70 percent of post-operative patients receive inadequate pain relief, including pediatrics patients." He says physicians probably underprescribe pain medications because they misunderstand the physiology of opiates, or they are overly concerned about addiction of issues surrounding addiction. "Addiction is actually an exceedingly rate phenomenom," Grigsby says. In a collaborative drug survey conducted in Boston hospitals during the early 1980s, some 12,000 post-surgical and post-trauma patients were surveyed for opiate addiction following treatment. Grigsby says the study showed only four patients met criteria for psychological dependence. Of those, three responded easily to intervention and only one had long-term difficulty with addiction to opiates.