The long term use effects of anti-depressiva

Antidepressants lead to emotional blunting in users: now it is finally clear why

In many cases, antidepressants do what they are supposed to do. But that comes at a price in some patients. Scientists now know why they feel emotionally blunted.
Depressed people feel down and no longer enjoy the things they normally enjoy. To solve their problem, they take antidepressants. In the Netherlands, approximately one million people are prescribed these drugs every year. This makes it one of the most commonly used drugs. Yet half of the users have a nasty side effect: they feel emotionally dulled. Scientists now think they know why: the resources have an effect on reinforcement learning, or our ability to learn through reward.

Happiness hormone and Reseach

Researchers from the universities of Cambridge and Copenhagen studied users of so-called selective serotonin reuptake inhibitors (SSRIs). These agents work on the level of serotonin, a neurotransmitter, also known as the happiness hormone. However, the antidepressants have an emotionally flattening effect in 40 to 60 percent of users, they report.
Cold and warm cognitionThe scientists got healthy test subjects to take escitalopram for a number of weeks to find out what impact the drug had on their performance. Of the 66 participants, 34 received a placebo and 32 received the antidepressant. They took the drug for at least 21 days and completed questionnaires about their emotions. They also had to take a number of tests to test their cognitive functions in terms of learning, decision-making and inhibitions.

There appeared to be no differences between the two groups in terms of 'cold' cognition, such as concentration and memory. And also with regard to 'warm' cognition, i.e. cognitive functions involving our emotions, there were hardly any differences.However, there was a difference in one important area: those who took the antidepressants were less good at reinforcement learning, compared to those who took the placebo. In reinforcement learning, we learn from our experiences through feedback from our environment, usually in the form of a reward.
To investigate this capacity for reinforcement learning, the scientists used a test in which participants were presented with two stimuli, A and B. If they chose A four out of five times, they received a reward. If they chose B, they only got a reward one out of five times. This rule was not explained to the subjects. They had to find out for themselves. In addition, the rule changed to the reverse at some point during the experiment and the participants had to be taught this new rule.

Less sex drive

The researchers found that those taking the antidepressant were less likely to use the positive and negative feedback to learn compared to the control group. This means that the drug affects their sensitivity to rewards and their ability to respond to them. The finding, the researchers say, may also explain why those taking escitalopram had more difficulty reaching orgasm during sex, a side effect frequently cited by patients.

Less pain and less pleasure

“Emotional dulling is a commonly cited side effect of SSRIs,” said Cambridge Professor Barbara Sahakian. “This is probably how they work: they take away some of the emotional pain that depressed people experience, but unfortunately, possibly some of the pleasure as well. Our study shows that this is because they are less sensitive to rewards, which provide important feedback.” Researcher Christelle Langley adds: “Our findings provide important evidence for the role of serotonin in reinforcement learning. We will now investigate how escitalopram affects the brain during this form of rewarding learning.”

What is Escitalopram? Escitalopram, also known under the brand name Sipralexa, is a selective serotonin reuptake inhibitor (SSRI). It is chemically similar to citalopram. SSRIs prevent serotonin from returning to the brain cells. They block, as it were, the reuptake of serotonin in neurons. As a result, more serotonin is released, which makes patients feel better. The difference with other antidepressants is that they only work on the serotonin level and not on other neurotransmitters. The drug is not completely harmless. In addition to affecting rewarding learning, as this study shows, it can also cause gastrointestinal complaints and headaches.

Source: "Chronic escitalopram in healthy volunteers has specific effects on reinforcement sensitivity: A double-blind, placebo-controlled semi-randomised study" - Neuropsychopharmacology