Specialists have figured out why various common antidepressants lead their users to experience emotional blunting. SciTechDaily reports that in a recent study, it was seen that drugs impact reinforcement learning, which is a vital behavioral process that enables individuals to learn from their environment.
SSRIs and Other Antidepressant Treatments
SciTechDaily reports that according to the NHS, there are over 8.3 million patients from England who have taken antidepressant treatments in2021 and 2022. Serotonin reuptake inhibitors (SSRIs) are particularly common antidepressants that are used to treat persistent or serious cases. Such drugs aim at serotonin, which is a neurotransmitter that delivers neural messages and has been referred to as the pleasure chemical. The most common types of SSRIs include Escitalopram (Lexapro), Citalopram (Celexa), Fluoxetine (Prozac), Paroxetine (Paxil, Pexeva), and Sertraline (Zoloft).
Blunting has been a widely reported side effect of SSRI usage. In such cases, patients reportedly feel emotionally dull and no longer find pleasure in the same way as before. UPMC reports that the phenomenon refers to feeling numbness towards both negative and positive emotions. Around 40% to 60% of SSRI users are thought to go through such side effects.
Most SSRI studies looked at their short-term usage. However, such drugs are usually used for chronic treatments.
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Why Do Antidepressants Lead to Emotional Blunting?
That being said, a research team led by those from the University of Cambridge collaborated with the University of Copenhagen to address such an issue. They recruited healthy volunteers and treated them with escitalopram, which is an SSRI that is acknowledged to be among the best-tolerated ones, for various weeks. They also looked into how the drug affected their performances based on cognitive assessments.
There were 66 volunteers who participated in the experiment. Out of the 66, 32 were given escitalopram, while the remaining 34 received placebos. Volunteers took the placebo or drug for a series of at least 21 days. They also completed self-report questionnaires and were issued various tests to evaluate cognitive aspects such as learning, executive function, inhibition, decision-making, and reinforcement behavior.
Findings were included in the Neuropsychopharmacology publication. The research team did not find any significant difference in terms of 'cold' cognition aspects like memory and attention. For 'hot' cognition, which refers to functions involving emotions, there were also no reported differences in the majority of tests.
A key finding, however, was that the escitalopram group exhibited decreased reinforcement sensitivity in two particular tasks. This was in comparison to the placebo group. Reinforcement learning refers to how individuals learn through feedback from the environment or from their own actions.
To examine reinforcement sensitivity, the scientists utilized a 'probabilistic reversal test.' In such a test, each participant will be provided with two different stimuli, A and B, that they can choose from. If they opted for A, for four out of five different times, they would be granted a reward. If they opted for B, they would only be rewarded once out of five times. Such a rule was not explicitly revealed to the participants. Moreover, at some point in the experiment, probabilities would alter and participants may need to learn the rules.
Reinforcement Sensitivity Affected by Antidepressants
The team discovered that the escitalopram group had lower likelihoods of using negative and positive feedback to guide task learning. This suggests how the drug affected how sensitive they are to rewards and how they respond to this.
Barbara Sahakian, senior author, Clarfe Hall Fellow, and professor of the Department of Psychiatry at the University of Cambridge, notes how emotional blunting is a prevalent side effect of SSRI antidepressant usage. Professor Sahakian notes that while the drugs take away emotional pain, it may also take away enjoyment of some sort. Based on the study, it is observed that this is because such users get less sensitive to reinforcement and rewards, which grant vital feedback.
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