Pain medicine : the official journal of the American Academy of Pain Medicine
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A recent US federal review and clinical guideline on opioids for chronic pain asserted that the literature contributes no evidence on efficacy because all trials had "inadequate duration." To explore the evidence, we examined durations of studies on opioid, nonopioid drug, and behavioral therapies for chronic pain. ⋯ No common nonopioid treatment for chronic pain has been studied in aggregate over longer intervals of active treatment than opioids. To dismiss trials as "inadequate" if their observation period is a year or less is inconsistent with current regulatory standards. The literature on major drug and nondrug treatments for chronic pain reveals similarly shaped distributions across modalities. Considering only duration of active treatment in efficacy or effectiveness trials, published evidence is no stronger for any major drug category or behavioral therapy than for opioids.