In one 2010 study cited in the new paper , Japanese researchers found that 78 percent of people trying to taper off Paxil suffered severe withdrawal symptoms. The research team had them taper much more slowly, over an average of nine months and for as long as four years. With this regimen, only 6 percent of subjects experienced withdrawal.

In another study, Dutch researchers in 2018 found that 70 percent of people who’d had trouble giving up Paxil or Effexor quit their prescriptions safely by following an extended tapering regimen, reducing their dosage by smaller and smaller increments, down to one-fortieth of the original amount. This is the regimen recommended in the new paper.

Dr. Horowitz and Dr. Taylor also cited brain-imaging evidence. Antidepressants such as Paxil, Zoloft and Effexor work in part by blocking the serotonin transporter, a molecule that works in the synapses between brain cells to clear out the chemical serotonin, which is thought to help impart a sense of well-being in some people. By blocking the transporter, antidepressants prolong and enhance serotonin’s effects.

But the brain-imaging studies found that inhibition of the transporter increases sharply with addition of the drug and, by extension, also drops sharply with any reduction in dosage. The standard medical advice, to reduce dosage by half — for instance, by taking a pill every other day — and end medication entirely after four weeks, does not take this into account, the two researchers argued.

“Doctors have in mind that these drugs act in a linear way, that when you reduce dosage by half, it reduces the effect in the brain by a half,” Dr. Horowitz said. “It doesn’t work that way. And as a result, there’s a huge load in terms of the effect on brain receptors, and patients are being advised to come off way too quickly.”

Laura Delano, executive director of Inner Compass Initiative, a nonprofit organization that runs The Withdrawal Project and focuses on helping people learn about safer psychiatric drug tapering, said: “I didn’t know about the benefits of slow tapering when I came off five meds in five months, and had a very difficult time in withdrawal.”

The new paper, she added, “speaks to how hard it is to get this information into the clinical world. We laypeople have been saying this for a long time, and it’s telling that it took psychiatrists coming off meds themselves for this information to finally be heard.”