That depends on which study you read and what kind of back pain you have.

In a review of 10 studies on back pain and antidepressants published recently by the Cochrane Collaboration, an international organization that reviews medical studies, Australian researchers found no clear evidence that antidepressants are more effective than sugar pills in helping patients with low-back pain. The finding is somewhat perplexing because, as the Australian researchers themselves noted, there is evidence that antidepressants can help with other types of chronic pain.

The Australian findings conflict with recent guidelines issued by the American Pain Society, which does recommend antidepressants for back pain, said Dr. Roger Chou [cq], director of the guideline program. But he cautioned in an email that antidepressants are not recommended as the “first line” treatment for low back pain partly because they can have side effects and partly because the benefit of antidepressants for back pain is “small to moderate.”

While some people may be surprised that antidepressants might alleviate pain, it actually makes sense, said Dr. Daniel Carr[cq], a pain specialist at Javelin Pharmaceuticals, Inc. in Cambridge. “We call a drug an antidepressant because it works against depression, but that doesn’t mean it can’t work against other conditions. A drug that influences processing in some parts of the brain can certainly influence other parts of the brain and spinal cord.”

“Back pain can be due to so many different conditions,” Carr said. “Antidepressants don’t help much with back pain that is caused by muscle spasms or by a spinal disc pressing on a nerve. But if the pain is caused by a nerve injury, such as nerves that were cut during surgery or chronic nerve pain from shingles or HIV, antidepressants are worth a try.”

Some antidepressants are more likely to help with back pain than others. The ones that help most are SNRIs, that is, drugs that increase levels of two neurotransmitters, serotonin and norepinephrine. Older antidepressants called tricyclics such as Elavil also help.

If your back pain persists more than a few weeks, it’s wise to see a doctor to figure out the cause and to see if antidepressants might help. That’s especially true if you have both back pain and depression, as many people do.

Untreated depression is a terrible disease, and antidepressants help millions of people. But they should be taken under tight medical supervision, said Dr. Alexander Bodkin, chief of clinical psychopharmacology research at McLean Hospital.

During the first few days of taking an SSRI-type antidepressant, many people feel intense agitation, even panic. This is actually “a sign that the SSRIs are on the way to making you better,” said Bodkin. But precisely because these feelings can be so scary, it is important for doctors to stay in close touch with patients and for patients to report any distress immediately.

Despite anecdotal reports of adverse reactions to antidepressants in children and adolescents, particularly SSRIs like Prozac and Zoloft, there are actually no cases of suicide related to taking antidepressants in all the pediatric clinical trial data that the US Food and Drug Administration re-evaluated in recent years, said Dr. John Mann, professor of psychiatry and radiology at Columbia University and director of research for the New York State Psychiatric Institute.

In a 2004 report, the FDA noted that spontaneous reports of suicidal thinking and nonfatal suicide attempts occurred at the rate of about 4 percent in young people taking antidepressants, and only 2 percent in those taking placebos. For this reason, the FDA made manufacturers put a “black box” warning on antidepressants for people up to age 18. But even during this time, noted Mann, who has done extensive research on the subject, “nearly all the suicides in children and adolescents were in people NOT taking antidepressants.”

New figures from the Centers for Disease Control and Prevention show that in the months after negative stories about antidepressants first came to light, the number of youth suicides actually went up — from 1,601 in 2003 to 1,828 in 2004 — after many years of declining numbers. This rise in youth suicides parallels a 20 percent drop in antidepressant prescriptions, Mann said.