New research showed that widely used antidepressants create "emotional blunting", which provides fresh insights into how the drugs may work and their potential negative effects.

The study discovered that after three weeks of taking a selective serotonin reuptake inhibitor (SSRI) medicine, healthy participants become less receptive to positive and negative feedback. 

"Blunting" could be part of how the medications help individuals recover from depression, but it could also explain a prevalent adverse effect.

The work’s senior author, Prof Barbara Sahakian of the University of Cambridge, stated, “In a way, this may be in part how they work. They take away some of the emotional pain that people who experience depression feel, but unfortunately it seems that they also take away some of the enjoyment.”

The findings could help patients make more educated pharmaceutical choices, she said, adding that "there is no doubt that antidepressants are useful" for many people.

According to the NHS, over 8.3 million people in England will get an antidepressant medication in 2021-22. SSRIs are among the most often used medications and are beneficial for the vast majority of patients, though not all.

Some persons on the medicine report feeling emotionally dull or that things are no longer as pleasurable, with one study estimating that this applies to 40-60% of those using the prescription. However, it is uncertain whether this symptom is a medicine side effect or a depression sign.

The most recent research argued that the medication can elicit emotional blunting on its own. In the study, 66 volunteers were given either the SSRI medicine escitalopram or a placebo for at least 21 days before participating in a battery of cognitive tests.

The medicine had no effect on nearly all tests, including that testing attention and memory. 

“The drug isn’t doing anything negative to cognition – from that point of view it’s very good,” said Sahakian.

Individuals on an SSRI, on the other hand, were less susceptible to reinforcement learning, which requires people to respond to positive or negative feedback.

On a screen, participants were offered two alternatives, A and B. Selecting A resulted in a prize four out of every five times while selecting B resulted in a reward one out of every five times.

People learn to select A after a few turns. The probabilities were shifted every now and again, and the participant was expected to learn the new rule. On average, the SSRI group was considerably slower to respond to these changes in feedback.

According to Sahakian, the findings could be beneficial to patients. “At least they can be aware of this. Some people can be offered different forms of treatment, particularly if they’ve not come into the hospital with severe illness,” he added.

Read next: No Health Without Mental Health