Patients Taking Antidepressants May Become Less Sensitive To Rewards: Research

Patients Taking Antidepressants May Become Less Sensitive To Rewards: Research

Commonly prescribed antidepressants can make patients less sensitive to rewards, affecting a key behavioral learning process that can lead to emotional boredom, according to the scientists.

Researchers have discovered that selective serotonin reuptake inhibitors, or SSRIs, can affect reinforcement learning, allowing people to learn from their actions and their environment.

These drugs work by targeting the body chemical known as serotonin, which carries messages between nerve cells in the brain.

A widely reported side effect of SSRIs is “numbing,” in which patients say they feel emotionally bored and are unable to respond with the same level of pleasure they normally would.

The experts said their findings, published in the journal Neuropsychopharmacology, show how serotonin affects reinforcement learning.

Professor Barbara Sahakian, from the Department of Psychiatry at the University of Cambridge, lead author of the study, said: “Emotional blunting is a common side effect of SSRI antidepressants.

“In a way, this may be partly how they work – they take away some of the emotional pain felt by people experiencing depression, but unfortunately it seems to take away some of the enjoyment as well.

“From our study, we can now see that this is because they become less sensitive to rewards, which provide important feedback.”

The researchers recruited 66 volunteers to participate in the experiment, 32 of whom received escitalopram while the rest received a placebo.

All participants completed a comprehensive set of self-report questionnaires after 21 days and were tested on cognitive functions including learning, inhibition, executive function, reinforcing behavior, and decision making.

The results indicated that there was reduced booster sensitivity in two tasks for the escitalopram group compared to those on placebo.

Participants taking escitalopram were less likely to use positive and negative feedback to guide their learning of the task compared with those taking placebo, the researchers said.

This suggests that the drug affected their sensitivity to rewards and their ability to respond accordingly, the team added.

But other experts have warned that patients taking SSRI drugs should not stop taking them based on this research.

Commenting 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 subjects, but it doesn’t change our understanding of antidepressants.

“People who are depressed may have difficulty feeling positive emotions such as happiness, making it difficult to differentiate between the effects of the condition and the effects of medication.

“By reducing negative feelings, antidepressants can help people get better.”

He added that antidepressants are an effective form of treatment for people experiencing depression that has a detrimental impact on their quality of life and where other treatments, such as talk therapies, have not worked.

Professor Pariante said: “Clinicians 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.

“Doctors should also periodically review their use to make sure they are still needed.

“We would not advise anyone to stop taking their antidepressants based on this study and we encourage anyone with concerns about their medication to contact their GP.”

NHS figures released in July showed that 8.3 million patients received antidepressants in 2021/22 in England, an increase of 6% from 7.9 million the previous year.

In 2019, research that looked at about 1,000 existing studies, published in JAMA Psychiatry, concluded that antidepressants are generally safe.

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