The commonly prescribed drugs can also make people less responsive to positive and negative feedback, and less sensitive to rewards.
According to the study, the drug helps by “blunting” negative emotions which may help with depression but has also been shown to affect a key behavioural learning process leading to emotional dullness.
How do antidepressants work?
Selective serotonin-reuptake inhibitors (SSRIs) are a class of drugs that are used as antidepressants.
SSRIs work by increasing serotonin levels in the brain, with serotonin working as a neurotransmitter influencing a person’s mood.
But according to the research, which was published in the journal Neuropsychopharmacology, serotonin can also affect reinforcement learning.
This was found after 66 volunteers received the SSRI drug escitalopram. or a placebo. and underwent a series of cognitive tests for at least 21 days.
Benefits from taking SSRI and escitalopram showed it didn’t affect the participants’ memory and attention. However, they were less responsive to positive or negative feedback, causing an “emotional dullness” among the SSRI participants.
Emotional blunting from antidepressants
“Emotional blunting is a common side effect of SSRI antidepressants,” said Professor Barbara Sahakian, from the department of psychiatry at the University of Cambridge.
She continued: “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.
“From our study, we can now see that this is because they become less sensitive to rewards, which provide important feedback.”
The latest research comes after another study, published in Molecular Psychiatry, found that depression was in fact not caused by a chemical imbalance further questioning antidepressants’ effectiveness.
According to the study, there is no clear evidence that depression is caused by low serotonin levels.
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 does not change our understanding of antidepressants.
“People who are depressed can struggle to feel positive emotions, such as happiness, which makes it difficult to differentiate between the effects of the condition and the effects of the medication.
“By reducing negative feelings, antidepressants can help people get better.”