A new study discusses the reason behind the emotional “blunting” that impacts around half of people who take SSRIs, a household of common antidepressant medications. The research study shows that the drugs effect reinforcement learning, a crucial behavioral process that enables us to gain from our surroundings.
Scientists have worked out why typical anti-depressants trigger around half of users to feel mentally blunted. In a research study published today, they show that the drugs impact support knowing, an important behavioral process that allows us to gain from our environment.
According to the NHS, more than 8.3 million patients in England received an antidepressant drug in 2021/22. Typical SSRIs include Citalopram (Celexa), Escitalopram (Lexapro), Paroxetine (Paxil, Pexeva), Fluoxetine (Prozac) and Sertraline (Zoloft).
Among the widely-reported side results of SSRIs is blunting, where clients report feeling emotionally dull and no longer finding things as satisfying as they used to. In between 40-60% of patients taking SSRIs are thought to experience this negative effects.
According to the NHS, more than 8.3 million patients in England received an antidepressant drug in 2021/22. A widely-used class of antidepressants, especially for persistent or severe cases, is selective serotonin reuptake inhibitors (SSRIs). Typical SSRIs consist of Citalopram (Celexa), Escitalopram (Lexapro), Paroxetine (Paxil, Pexeva), Fluoxetine (Prozac) and Sertraline (Zoloft).
Professor Barbara Sahakian, senior author, from the Department of Psychiatry at the University of Cambridge and a Fellow at Clare Hall, stated: “Emotional blunting is a typical side impact of SSRI antidepressants. In a way, this may be in part how they work– they take away some of the emotional pain that individuals who experience anxiety feel, however, unfortunately, it seems that they likewise take away some of the pleasure.
To date, most research studies of SSRIs have actually just analyzed their short-term usage, however, for medical use in depression, these drugs are taken chronically, over a longer amount of time. A group led by researchers at the University of Cambridge, in partnership with the University of Copenhagen, sought to address this by administering and hiring healthy volunteers escitalopram, an SSRI known to be one of the best-tolerated, over a number of weeks and examining the impact the drug had on their performance on a suite of cognitive tests.
In overall, 66 volunteers participated in the experiment, 32 of whom were given escitalopram while the other 34 were provided a placebo. Volunteers took the drug or placebo for a minimum of 21 days and completed a comprehensive set of self-report questionnaires and were provided a series of tests to evaluate cognitive functions including learning, inhibition, executive function, reinforcement behavior, and decision-making.
The results of the research study are published today (January 23, 2023) in the journal Neuropsychopharmacology.
The group found no substantial group distinctions when it pertained to cold cognition– such as attention and memory. There were no differences in the majority of tests of hot cognition– cognitive functions that involve our feelings.
However, the crucial unique finding was that there was reduced support sensitivity on two jobs for the escitalopram group compared to those on placebo. Support learning is how we gain from feedback from our actions and environment.
In order to evaluate reinforcement sensitivity, the scientists utilized a probabilistic reversal test. Volunteers would not be informed this guideline, but would have to learn it themselves, and at some point in the experiment, the possibilities would change and participants would need to discover the brand-new guideline.
The group discovered that individuals taking escitalopram were less most likely to use the positive and negative feedback to assist their learning of the task compared to individuals on placebo. This suggests that the drug impacted their level of sensitivity to the benefits and their ability to respond appropriately.
The finding may also discuss the one distinction the group found in the self-reported questionnaires, that volunteers taking escitalopram had more trouble reaching orgasm when making love, a side effect typically reported by patients.
Teacher Barbara Sahakian, senior author, from the Department of Psychiatry at the University of Cambridge and a Fellow at Clare Hall, stated: “Emotional blunting is a common side effect of SSRI antidepressants. In a way, this may be in part how they work– they remove some of the psychological pain that people who experience depression feel, but, unfortunately, it appears that they likewise remove some of the pleasure. From our research study, we can now see that this is since they end up being less delicate to benefits, which provide crucial feedback.”
Dr. Christelle Langley, joint very first author also from the Department of Psychiatry, included: “Our findings supply crucial proof for the role of serotonin in reinforcement learning. We are following this work up with a research study examining neuroimaging data to comprehend how escitalopram affects the brain during benefit learning.”
Reference: “Chronic escitalopram in healthy volunteers has specific effects on reinforcement level of sensitivity: A double-blind, placebo-controlled semi-randomised study” by Langley, C, Armand, S, et al., 23 January 2023, Neuropsychopharmacology.DOI: 10.1038/ s41386-022-01523-x.
The research study was funded by the Lundbeck Foundation.