Ideally, the medical decisions doctors make for their patients should be free of any outside influence.

But for regular readers of this blog, we know that’s not always the case.

A 2010 HealthLeaders Media Industry Survey identifies some factors that may influence a physician’s medical decision. Here are some of the results.

Pressure from patients was a significant influence, with only 17.9% of doctors saying it wasn’t a factor. Doctors often encounter patients who “demand a drug he saw advertised on television or ask for an extra test ‘just to be safe.'” When it comes to controlling costs, patient pressure is an underpublicized, yet significant, phenomenon.

Coming second is fear of lawsuits, which is unsurprising. One-third of doctors called it a “major influence,” more than any other factor. Health reformers who ignore defensive medicine is leaving a significant means of cost control on the table.

And, as I’ve mentioned previously, malpractice reform doesn’t have to include non-economic caps. The suggestion that doctors who follow evidence-based guidelines (which progressive reformers endorse, by the way) be protected from lawsuits is a good one.

The physician payment system, which encourages “more” medicine through a fee-for-service payment system contributes the third influence. Divorcing reimbursement from quantity of care can reduce this, but unfortunately, it’s nowhere to be found in the current reform plans.

And finally, pressure from administrators represents, surprisingly, the least influential factor. According to the study, “this reflects the greater emphasis placed on physician-hospital alignment in recent years, and the growing number of physicians who are employed by hospitals and health systems.”

There you have it. So when your doctor suggests a treatment option for you, it’s likely that one or more of these factors is contributing to the decision.