“The popularity of the ‘chemical imbalance’ theory of depression has coincided with a large increase in antidepressant use. Antidepressant prescriptions have increased dramatically since the 1990s, with one in six adults in England and 2% of adolescents who are prescribed an antidepressant in a given year. “
“Many people take antidepressants because they have been led to believe that their depression has a biochemical cause, but this new research suggests that this belief is not based on evidence.”
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The umbrella review aimed to capture all relevant studies that have been published in the major research fields on serotonin and depression. The review included tens of thousands of participants.
Research comparing serotonin levels and their degradation products in the blood or brain fluids found no difference between people diagnosed with depression and participants in healthy control (comparison).
Research on serotonin receptors and the serotonin transporter, the protein targeted by most antidepressants, found weak and inconsistent evidence suggesting higher levels of serotonin activity in people with depression. However, the researchers say the findings are likely to be explained by the use of antidepressants among people diagnosed with depression, as these effects were not reliably ruled out.
The authors also analyzed studies in which serotonin levels were artificially reduced in hundreds of people by depriving their diets of the amino acid needed to produce serotonin. These studies have been cited to show that a serotonin deficiency is related to depression. However, a meta-analysis conducted in 2007 and a sample of recent studies found that reducing serotonin in this way did not produce depression in hundreds of healthy volunteers. There was very weak evidence in a small subgroup of people with a family history of depression, but this involved only 75 participants, and the most recent evidence was inconclusive.
Very large studies with tens of thousands of patients analyzed gene variation, including the serotonin transporter gene. They found no difference in these genes between people with depression and healthy controls. These studies also looked at the effects of life’s stressful events and found that these had a strong effect on people’s risk of depression: the more stressful events a person would have experienced, the more likely they were to become depressed. A famous initial study found a relationship between stressful events, the type of serotonin transporter gene a person had, and the possibility of depression. But larger, more exhaustive studies suggest it was a false finding.
These findings jointly led the authors to conclude that “there is no support for the hypothesis that depression is caused by decreased activity or serotonin concentrations.”
Researchers say their findings are important, as studies show that between 85% and 90% of the public believe that depression is caused by low serotonin or a chemical imbalance. A growing number of scientists and professional bodies recognize the framing of the chemical imbalance as an oversimplification. There is also evidence that believing that low mood is caused by a chemical imbalance makes people have a pessimistic view of the likelihood of recovery and the ability to manage mood without medical help. This is important because most people will meet the criteria for anxiety or depression at some point in their lives.
The authors also found evidence from a large meta-analysis that people using antidepressants had lower levels of serotonin in their blood. They concluded that some evidence was consistent with the possibility that long-term use of antidepressants would reduce serotonin concentrations. Researchers say this may imply that the increase in serotonin produced by some antidepressants in the short term could cause compensatory changes in the brain that produce the long-term opposite effect.
Although the study did not review the effectiveness of antidepressants, the authors encourage more research and advice on treatments that could focus on managing stressful or traumatic events in people’s lives, such as psychotherapy, together. with other practices such as exercise or awareness, or addressing underlying contributors such as poverty, stress, and loneliness.
Professor Moncrieff said: “Our view is that patients should not be told that depression is caused by low serotonin or a chemical imbalance, and they should not be made to believe that antidepressants work by addressing “We don’t understand exactly what antidepressants do in the brain, and giving people this kind of misinformation prevents them from making an informed decision about whether or not to take antidepressants.”
The co-author, Dr. Mark Horowitz, a trained psychiatrist and clinical researcher in psychiatry at UCL and NELFT, said: “I had been taught that depression was caused by low serotonin in my training in psychiatry and I had even taught students on my own. lectures. Being involved in this research was revealing and it seems to me that everything I thought I knew would have been turned upside down. “
“An interesting aspect of the studies we examined was the strong effect that life’s adverse events had on depression, suggesting that low mood is a response to people’s lives and cannot be reduced. to a simple chemical equation “.
Professor Moncrieff added: “Thousands of people suffer from side effects of antidepressants, including the severe withdrawal effects that can occur when people try to stop them, but prescription rates continue to rise. We believe this situation has been motivated. partly because of the false belief that depression is due to a chemical imbalance. It is time to inform the public that this belief is not based on science. ”
Researchers warn that anyone considering withdrawing from antidepressants should seek the advice of a healthcare professional, given the risk of adverse effects after withdrawal. Professor Moncrieff and Dr. Horowitz are conducting ongoing research on how best to gradually stop taking antidepressants.
Source: Eurekalert
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