Patients taking antidepressants may be less sensitive to rewards – research
Frequently prescribed antidepressants can make patients less sensitive to rewards — which researchers say disrupts an important behavioral learning process that can lead to emotional decline.
Researchers have found that selective serotonin reuptake inhibitors, or SSRIs, can affect reinforcement learning, which allows people to learn from their actions and their surroundings.
These drugs work by targeting the body’s “feel good” chemical known as serotonin, which carries messages between nerve cells in the brain.
A commonly reported SSRI side effect is “deafening”, with patients saying they feel emotionally drained and unable to respond with the same level of joy as they normally would.
The experts said their findings, published in the journal Neuropsychopharmacology, show how serotonin affects reinforcement learning.
Professor Barbara Sahakian of the University of Cambridge’s Department of Psychiatry – who is senior author of the study – said: “Emotional depression is a common side effect of SSRI antidepressants.
“In a way, they may work that way in part – they take away some of the emotional pain that people with depression feel, but unfortunately they also seem to take away some of the pleasure.”
“From our study, we can now see that this is because they are less sensitive to rewards that provide important feedback.”
The researchers recruited 66 volunteers to take part in the experiment, 32 of them received escitalopram while the rest received a placebo.
All participants completed a comprehensive set of self-report questionnaires after day 21 and were tested for cognitive functioning including learning, inhibition, executive function, reinforcement behaviors, and intake of decisions.
The results showed that there was a reduction in reinforcement sensitivity on two tasks in the escitalopram group compared to placebo.
The researchers said that participants who took escitalopram made less use of positive and negative feedback to guide their learning of the task compared to those on placebo.
This suggests that the drug affected their sensitivity to rewards and their ability to respond appropriately, the team added.
However, other experts have warned that patients taking SSRI drugs should not stop them based on this research.
Speaking on behalf of the Royal College of Psychiatrists, Professor Carmine Pariante, who was not involved in the study, said: “This is an interesting and well-conducted study in healthy volunteers, but it does not change the our understanding of antidepressants.
“People who are depressed can have difficulty feeling positive emotions such as happiness, which makes it difficult to distinguish between the effects of the condition and the effects of the medication.
“By reducing negative feelings, antidepressants can help people get better.”
He added that antidepressants are an effective form of treatment for people suffering from depression that adversely affects their quality of life and for whom other treatments, such as B. talk therapy, have not worked.
Professor Pariante said: “Doctors should always discuss the risks and potential benefits of taking antidepressants with their patients, as we know that their effectiveness can vary from person to person.
“Clinics should also regularly review their use to ensure they are still needed.
“We do not advise anyone to stop taking their antidepressants based on this study and I encourage anyone with concerns about their medication to contact their doctor.”
NHS figures released in July showed that 8.3 million patients were receiving antidepressants in England in 2021/22, up 6% from 7.9 million the previous year.
In 2019, a review of approximately 1,000 existing studies published in JAMA Psychiatry concluded that antidepressants are generally safe.