Long-term antidepressants may offer limited benefits while posing health risks, according to a study calling for treatment reviews every six months.
Researchers said prolonged use of the medicines has been linked to sexual dysfunction, emotional numbing, cognitive impairment and weight gain.
They also warned that stopping antidepressants after long-term use can trigger withdrawal symptoms that may last for months or, in some cases, years.
Mark Horowitz, a psychiatrist at Adelaide University and author of the study, said evidence supporting long-term use may be less clear than previously thought.
“Much of the evidence supporting long-term antidepressant treatment comes from so-called relapse prevention trials,” Dr Horowitz said.
“These studies typically compare patients who continue medication with those who stop abruptly or rapidly.”
“Because they don’t distinguish between withdrawal symptoms and the return of depression, we believe many apparent relapses may actually be withdrawal effects.”
More than 330m people globally live with depression, and a significant proportion take antidepressants every day.
Nearly twice as many women take antidepressants as men.
The study said most people taking antidepressants in high-income countries, including the US, UK and Australia, use them over the long term.
It also said a growing body of research suggests commonly prescribed antidepressants do not work by correcting an underlying deficiency of serotonin, a brain chemical involved in mood and several other functions.
Researchers said short-term trials show antidepressants bring only small improvements compared with placebos.
The study said symptoms such as anxiety, low mood and insomnia can occur both when antidepressants are withdrawn and when depression returns.
Dr Horowitz said this could mean withdrawal effects are being counted as depression relapse in some research.
“Symptoms such as anxiety, low mood and insomnia occur in both withdrawal from antidepressants and a return of depression,” he said.
“As these studies do not distinguish between them, they will miscategorise withdrawal as a return of depression, as this is the focus of such studies.”
The researchers called for clinical guidelines to be updated to reflect that there are no good studies showing the effectiveness of taking antidepressants in the long term.
They also said treatment should be reviewed every six months, with patients supported to make informed decisions about whether to continue.
“Concerningly, the risk of withdrawal effects appears to increase with the duration of use, one reason for stopping antidepressants sooner rather than later,” Dr Horowitz said.
Katharine Wallis, another author of the study from the University of Queensland Medical School, said patients should be supported if they choose to stop treatment.
“There is increasing emphasis on supporting patients to make informed choices about antidepressant use and to stop antidepressants by slowly decreasing the dose,” she said.