Research performed at the Mayo Comprehensive Pain Rehabilitation Center and presented to the American Society of Anesthesiologists at their 2007 annual meeting found that low vitamin D levels may be associated with chronic pain. Researchers found that about 26% of patients with chronic pain also have low vitamin D levels. The researchers found that patients with low vitamin D levels also needed higher dosages of pain medication. The group with low vitamin D needed twice as much morphine when compared to those with normal vitamin D levels. The researchers believe that vitamin D deficiency may not be the principle cause of pain, but may be a complicating factor.