Though antidepressants are a common treatment for depression, psychiatrists still don’t have a clear understanding of how exactly they work. A new paper suggests that some explanations persist thanks to clever marketing, despite a lack of scientific evidence.

On Tuesday, David Healy, a professor of psychiatry at Bangor University in Wales and author of Let Them Eat Prozac, published an opinion piece in the journal The BMJ writing that the link between serotonin and depression is a “myth” that continues to be perpetrated by the pharmaceutical industry. Specifically, Healy says the marketing of selective serotonin re-uptake inhibitors—better known as SSRIs—has been problematic.

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“Drug companies marketed SSRIs for depression even though they were weaker than older tricyclic antidepressants, and sold the idea that depression was the deeper illness behind the superficial manifestations of anxiety,” he writes. “The approach was an astonishing success, central to which was the notion that SSRIs restored serotonin levels to normal, a notion that later transmuted into the idea that they remedied a chemical imbalance.”

While Healy has been described by some of his peers as an iconoclast, many members of the psychiatry community agree with him. “He’s preaching to the choir at this point,” says Dr. Victor I. Reus, a professor in the department of psychiatry at the University of California, San Francisco.

Reus adds that it’s not that SSRIs don’t work (though there are certainly some who do make that argument). Rather, it’s how they are marketed that is largely overblown. “My experience and belief is that they do work, but we don’t have a comprehensive and holistic understanding of why they work,” he says. “But I think [they] are in many cases remarkably successful even without understanding why they are so.”

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The idea that SSRIs restore abnormal serotonin levels in the brain isn’t substantiated by research, so why does that line of thinking persist? According to Healy, the idea was adopted by physicians and patients as an easy way to communicate the confounding disorder and its treatment. That’s led to what he calls a costly distraction away from other depression drug research. Meanwhile, many other depression treatments have no effect on serotonin but can be effective against the condition, whereas some people who take SSRIs do not, in fact, get better.

“I think in essence the article raises a point that you have to think beyond SSRIs. They are not industry’s gift for the treatment of depression,” says Dr. Norman Sussman, a professor in the department of psychiatry at New York University Langone Medical Center. Some of the older drugs may actually work better with fewer qualit- of-life-impairing effects.”

Healy does not say that serotonin plays no role in the treatment of depression, writing that the compound is “not irrelevant,” but that the market boom of SSRIs raises questions about why physicians would put aside clinical trial evidence in place of “plausible but mythical” accounts of biology.

“My feeling is that these drugs maybe don’t work as well for depression as they do for other things like obsessiveness and anxiety,” says Sussman. “There are some people that do well on them but most of the evidence that’s come out recently is that they seem to work best in people that are the most depressed.”

Sussman says that SSRIs are often prescribed in primary care for people who have mild depression.

“You wonder what the real risk benefit ratio is in that population,” he says. “They’ve been oversold.”

Read next: Why Kids Who Believe in Something Are Happier and Healthier

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