Most cancer doctors say they don't know enough about medical marijuana to provide an informed opinion to patients.

Nevertheless, many go ahead and give its use their blessing, a national survey reveals.

Seven out of 10 oncologists surveyed in the United States said they aren't informed enough about the risks and benefits of medical marijuana to recommend its use to patients, according to findings published May 10 in the Journal of Clinical Oncology.

But eight out of 10 cancer doctors said they've discussed medical marijuana with patients in the past year, and 46 percent have gone so far as to recommend its use in cancer treatment.

This is a "concerning discrepancy," said Dr. Ilana Braun, chief of Dana-Farber Cancer Institute's division of adult psychosocial oncology, in Boston.

"We can think of few other instances in which physicians would offer clinical advice about a topic on which they do not feel knowledgeable," Braun said.

Currently, there are 30 states with medical marijuana laws on the books, and almost all name cancer as a qualifying condition for its use, Braun said.

However, pot remains an illegal substance under federal law, restricting research opportunities into its effectiveness as a medical treatment. "The scientific evidence base supporting use of medical marijuana in oncology remains thin," Braun said.

To assess how cancer doctors are grappling with this issue, Braun and her colleagues surveyed a nationally representative random sample of 400 oncologists.

The responses revealed that:

  • Only 30 percent of cancer doctors felt sufficiently informed to make recommendations regarding medical marijuana.
  • About 46 percent recommended its use, regardless.
  • Of those who recommended its use, 56 percent admitted that they did not consider themselves well-informed enough to have done so.

Braun said more research needs to be done regarding the medical effectiveness of marijuana, as well as potential harmful effects.

For example, patients with immune systems wrecked by chemotherapy could be at increased risk of a fungal infection from pot use, she noted.

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