The drugs we call antidepressants are fast becoming a misnomer. In fact, doctors regularly prescribe off-label uses for unrelated conditions they weren't designed or approved to treat, ranging from weight loss to incontinence.

One study published last year in the Journal of the American Medical Association revealed that nearly half of antidepressant prescriptions electronically recorded in Quebec, Canada were intended to treat other conditions, and a third were used to treat conditions they hadn't received any approval for from regulatory agencies.

Now, the researchers behind that study have gone one step further and looked at whether these prescriptions were reasonable to dole out in the first place. Their verdict, published recently in the BMJ, isn't particularly kind.

Using the same prescription database from Quebec, the researchers from Montreal and Boston found that only one-sixth of off-label antidepressant prescriptions had strong, direct scientific proof justifying its use. Forty percent of the time, there was strong evidence for the off-label use of a drug in the same class as the prescribed drug, though not for the prescribed drug itself. And 44 percent of off-label prescriptions had no good evidence, direct or not, for its use.

"The major takeaway is that we need to more closely examine the way we use antidepressants and be more cautious and conservative about taking these drugs when there is insufficient evidence to suggest they are effective for treating certain conditions," lead author Dr. Jenna Wong of McGill University told Vocativ in an email. Given that the U.S. and Canada have similar prescribing practices, she added, it's likely the U.S. has its own off-label problem.

Common off-label uses for antidepressants in the study included nerve pain, insomnia, and anxiety. But only three prescribed drug-condition pairs had any strong backing behind them, defined by the researchers as being regularly recommended for most people with the condition and supported by at least one randomized clinical trial. That included the drug amitriptyline, an older antidepressant now also used for nerve pain, and venlafaxine, a newer, safer drug that's shown success in treating obsessive compulsive disorder.

Off-label use isn't inherently nefarious, of course. Oftentimes, doctors prescribe drugs off-label not out of carelessness, but because their patients' insurance plans won't cover the recommended drug; because the off-label drug may have less side effects overall; or as a last resort for a condition that hasn't responded to anything else.

But there's simply a lot less we know about how patients will respond to an unfamiliar drug. Patients may be getting the glorified version of a worthless placebo pill, or at worst, they may suffer unforeseen side effects from the drug itself or from interactions with other drugs they're taking.

Because drug testing is such an expensive process, though, it's unlikely that many off-label uses will ever have much evidence behind them. In spite of that, Wong does think there are ways to make off-label prescribing safer. Thanks to the growing rise of electronic prescription systems and health records, doctors could have warnings pop up whenever they decide to prescribe an off-label drug with little evidence. And these systems could also serve as a way to coordinate and keep track of patients and doctors who willfully choose to take the plunge regardless.

"At the first sign of concern, such systems would communicate this information back to physicians, almost like a feedback loop so that physicians can constantly re-evaluate their prescribing decisions based on the latest evidence," Wong said.

This article originally appeared at Vocativ.com: When antidepressants are used to treat everything but depression.