Emotional Blunting From Antidepressants? Researchers Shed Light On Phenomenon

Some people on certain antidepressant medicines tend to feel "blunted" emotionally, and scientists are now able to explain why this might happen.

For their study, published Monday in Neuropsychopharmacology, a team of researchers conducted a study to examine the impacts of antidepressant escitalopram on cognition. Escitalopram is a selective serotonin reuptake inhibitor (SSRI) that's typically used to treat conditions like major depressive disorder and anxiety.

One of the common side effects of such SSRIs is called the "blunting" effect — a condition where the person is unable to feel the same level of pleasure that they used to, the University of Cambridge noted in a release, adding that as much as 40 to 60% of patients experience it.

"Given that SSRIs are administered chronically in the treatment of neuropsychiatric disorders, it is particularly important to understand the long-term effects of SSRI administration on cognition," the researchers wrote. "Currently, only a few studies have examined SSRIs administered sub-chronically, over approximately 7 days."

To shed light on the matter, the researchers conducted a study involving 66 healthy volunteers. 32 of them received 20 mg of escitalopram daily, while the remaining 34 participants were given a placebo for at least 21 days, for an average of 26 days. They answered questionnaires and participated in a battery of neuropsychological tests assessing their cognitive functions.

The researchers didn't find differences in "cold" (rational and non-emotional) or "hot" (social and emotional) cognition between the groups. However, they did notice that escitalopram "reduced reinforcement sensitivity" when compared to the placebo.

Reinforcement sensitivity, the researchers explained, is "the degree to which a participant is driven by their reinforcement history." In the test, for instance, the participants were presented with two stimuli — A and B. A reward was given for choosing A "four out of five times," noted the University of Cambridge. But choosing B only yielded a reward "one time out of five."

The participants were unaware of the rule and had to work it out themselves.

The results showed that those who were on escitalopram were less likely to use positive reinforcement to guide their understanding of the task, the university noted. In other words, it appears that they may have become "less sensitive to rewards," and this, in turn, may have affected their response.

This lower sensitivity to reinforcement may be reflecting the blunting effect reported by those on the treatment, the researchers said,

"Emotional blunting is a common side effect of SSRI antidepressants," study senior author, Professor Barbara Sahakian of the University of Cambridge, said in the release. "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."

"These novel findings provide strong evidence for a key role of serotonin in reinforcement learning," the researchers wrote.

The study sheds light on how such antidepressants may be playing a role in the emotional blunting that some patients tend to experience. That doesn't mean, however, that those who need such medications should stop taking them.

Other experts not involved in the study also stated the importance and benefits of such antidepressants, noting that they can "help people get better."

"This is an interesting and well-conducted study in healthy subjects, but it does not change our understanding of antidepressants," Professor Carmine Pariante, speaking on behalf of the Royal College of Psychiatrists, said as per PA Media.

"Practitioners should always discuss the potential risks and benefits of taking antidepressants with their patients as we know their effectiveness can vary from person to person. We would not recommend for anyone to stop taking their antidepressants based on this study and encourage anyone with concerns about their medication to contact their GP."