Widely used antidepressants cause “emotional dullness” according to research that offers new insights into how drugs may work and their potential side effects.
The study found that healthy volunteers were less responsive to positive and negative feedback after taking a selective serotonin reuptake inhibitor drug (SSRIs) for three weeks.
emotional blunting
The “dullness” of negative emotions could be part of how medications help people recover from depression, but it could also explain a common side effect.
Lead author of the paper, Professor Barbara Sahakian from the University of Cambridge, said: “In a way, this may be partly how they work. They take away some of the emotional pain that people experiencing depression feel, but unfortunately they seem to take away some of the enjoyment as well.”
Findings
The findings could help patients make better informed decisions about their medications, he said, but added that “There is no doubt that antidepressants are beneficial” for many patients.
According to the NHS, more than 8.3 million patients in England received an antidepressant medicine in 2021-22. The SSRIs are among the most widely used and are effective for most patients, although not all.
Some people taking the drug report feeling emotionally bored or not finding things so pleasurable anymore, and one study suggests this applies to 40-60% of people taking the drug. However, it has not been clear whether this symptom is a side effect of the medication or a symptom of depression.
latest investigation
The latest work suggests that the drug alone can produce emotional numbing. In the study, published in the journal Neuropsychopharmacology, 66 volunteers were given the SSRI drug escitalopram or a placebo for at least 21 days before taking a series of cognitive tests.
In almost all tests, including those that assess attention and memory, the drug made no difference. “The drug is not doing anything negative for cognition; from that standpoint, it’s very good,” Sahakian said.
effort learning
However, people who took the SSRIs were less responsive to reinforcement learning, which requires people to respond to either positive or negative feedback. Participants were shown two options on a screen, A and B. Selecting A would result in a reward four out of five times, while B was only rewarded one out of five times.
After a few turns, people learn to select A. From time to time, the probabilities were changed and the participant was required to learn the new rule. The SSRI group was, on average, significantly slower to respond to these changes in feedback.
In the questionnaires, volunteers taking escitalopram also reported having more trouble reaching orgasm when having sex, which is another side effect that patients often report.