A new study has found that sertraline (sold as Zoloft among other names), despite being marketed as an antidepressant, may be ‘unlikely’ to treat depressive symptoms within six weeks, but does show improvements in anxiety when taken.

The PANDA study, a pragmatic, multicentre, double-blind, placebo-controlled randomised trial of patients from 179 primary care surgeries in four UK cities, included patients aged 18 to 74 years who had depressive symptoms of any severity or duration in the past two years and found no evidence that sertraline led to a clinically meaningful reduction in depressive symptoms at six weeks.

The mean six-week PHQ-9 score was 7.98 in the sertraline group and 8.76 in the placebo group, whereas evidence that sertraline led to reduced anxiety symptoms, better mental (but not physical) health-related quality of life, and self-reported improvements in mental health was observed.

The findings support the prescription of SSRI antidepressants in a wider group of participants than previously thought, including those with mild to moderate symptoms who do not meet diagnostic criteria for depression or generalised anxiety disorder.

Professor Glyn Lewis, head of division at UCL Psychiatry, who led the study, said: “Antidepressants work but perhaps in a different way to the way we had originally thought. They seem to be working on anxiety symptoms first before any smaller, and later, possible effects on depression.

“We definitely need better treatments for depression – we need more research in this area. This is an unexpected result. Our primary hypothesis was that it would affect those depressive symptoms at six weeks and we didn’t find that. So it is an unexpected finding.”

Depression is a major contributor to the global burden of disease and by 2030 is predicted to be the leading cause of disability in high-income countries. Prescriptions for antidepressants have risen dramatically in high-income countries over the past decade (70.9 million items were prescribed in England in 2018), leading to concerns that they are overprescribed.