A new study found that antidepressants may make it more difficult for users to feel both positive and negative emotions.
New insights have emerged into the long-misunderstood function of antidepressant drugs, which may cause users to experience “emotional blunting,” according to a recent study in Neuropsychopharmacology.
“Emotional blunting is a common side effect of SSRI antidepressants,” said lead author Professor Barbara Sahakian of the University of Cambridge. “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.”
“From our study, we can now see that this is because they become less sensitive to rewards, which provide important feedback,” she added.
Antidepressants are a $17 billion a year industry that is set to grow to nearly $22 billion per year by 2027. Figures show that approximately 13% of American adults take antidepressants annually, but the rate is much higher for women, almost 18% of whom are prescribed the medication.
The study comes as researchers have been trying to understand exactly how antidepressants help people, after a systematic umbrella review last summer finally put to rest the longstanding “chemical imbalance” narrative, which posits that depression is caused by serotonin abnormalities in the brain.
Doctors report witnessing improvement in some of their patients on the medication, but the mechanism responsible for the improvement, if any, is unclear. This new study provides insight into their function, which may be beneficial to people who struggle with mood regulation.
In the study, 66 volunteers were given either the selective serotonin reuptake inhibitors (SSRI) drug, escitalopram, or a placebo for 21 days. Questionnaires were completed before and after the trial period, and neuropsychological tests were administered to study their cognitive function. Blood tests ensured the participants in the escitalopram group took the medicine.
In questionnaires, the participants taking the drug reported having more trouble achieving an orgasm while having sex — a side-effect often reported by antidepressant users. The findings could be useful for patients to make better informed decisions about their treatment plan, and whether or not the purported benefits of antidepressants may be worth the side effects.
“At least they can be aware of this,” Sahakian said. “Some people can be offered different forms of treatment, particularly if they’ve not come into hospital with severe illness.”
When the team administered a “learning task” test to participants, they found that those in the antidepressant group had a lesser response to positive and negative feedback than the control group, which suggested the drug affected their sensitivity to rewards.
In another battery of tests that assessed attention and memory, they found the drug made no difference. “The drug isn’t doing anything negative to cognition — from that point of view it’s very good,” said Sahakian.
Dr. Christelle Langley, another lead author on the study from the University of Cambridge, added: “Our findings provide important evidence for the role of serotonin in reinforcement learning. We are following this work up with a study examining neuroimaging data to understand how escitalopram affects the brain during reward learning.”