Depression may not be linked to low serotonin, new analysis discovers

The Serotonin hypothesisStates that a chemical imbalance in the brain, including a deficiency of serotonin, proposed decades ago causes depression.

The most common antidepressants, known as selective serotonin reuptake inhibitors (SSRIs), are thought to make serotonin more accessible in the brain. Block reabsorption Conversion of serotonin to neurons.

But in their recent analysis, Joanna Moncliffe, MDA professor of psychiatry at the University College London and her colleagues, found that there was no “consistent evidence” that serotonin was involved in depression.

Their findings published on July 20 Molecular psychiatry,It contains:

• Studies of serotonin and its degradation products in blood and brain fluid have found that the levels of these chemicals are similar in people with and without depression.
• Studies on serotonin receptors and the serotonin transporter, a protein targeted by many antidepressants, provide “weak and inconsistent” evidence that people with depression have higher levels of serotonin activity. Did.
• Studies in which serotonin levels in healthy people were artificially lowered by a special diet found that this did not increase their risk of developing depression.
• Genetic studies showed no difference in serotonin-related genes between depressed individuals and healthy participants.

“After decades of extensive research, there is no convincing evidence that depression is caused by abnormalities in serotonin, especially decreased levels or activity of serotonin,” said Moncliffe. increase. news release..

Dr. Anthony KingNeuroscientists and qualified psychologists and psychotherapists at Ohio State University School of Medicine who were not involved in the new review agree that the role of serotonin in depression is exaggerated.

“The idea that depression is a chemical imbalance characterized by synaptic serotonin deficiencies or low levels is incorrect,” he said. “It was never, and it isn’t.”

But “I’m not saying that serotonin isn’t involved, and I’m not saying that SSRIs are useless,” he added.

He said serotonin is likely to be involved in some way, but the relationship between depression and other brain chemicals is complex. Similarly, he said SSRIs can help some people — not just everyone.

King also agreed that stress could play a role in the development of depression.

King also said that stress can play a role in the development of depression.

Dr. SriyansenA professor of depression and neuroscience at the University of Michigan and director of Francis Kenneth Eisenberg and the Center for Family Depression, he said he did not believe the new review would completely eliminate serotonin from the picture.

“Whether serotonin is somehow involved in depression is an open question,” he said. “The brain is so complex and complex that it would be surprising if serotonin wasn’t involved at all.”

He pointed out recently Meta-analysis The results of a study examining the association between serotonin-related genetic mutations, stress, and depression as evidence that the serotonin case is not closed.

In that study, researchers found that people with certain serotonin-related gene variants were at increased risk of developing depression in response to stressful life events. However, this was only true for chronic stress and depression assessed within a year of stressors.

This meta-analysis was published this month and was not included in the review by Moncrieff and her colleagues.

However, there is one thing Sen agrees with Moncreiff and her colleagues.[Chemical imbalance] It’s not an exact representation of our understanding of what’s happening in the brain, “he said.

“It’s likely that there are significant modified specific circuits and connection loops in the brain,” he said. “But I don’t know exactly what’s going on.”

King said there are other ways to think about depression that can help people get out of the downward spiral that often accompanies this condition.

“”[Stressful life events] It can lead to emotional upset and major changes, “he said. “It can be accompanied by a kind of pessimism and certain habits of behavior and thinking.”

Basically, “people fall into ruts — they fall into ruts mentally and behaviorally,” he said. “And the sense of inertia begins.”

This may sound like a difficult cycle to get out of, but King said that some types of treatment can help people move again. Cognitive behavioral therapy, Behavioral activationWhen Mindfulness..

The new review also argued whether talking about SSRIs would help to correct chemical imbalances.

“Many people are taking antidepressants because they are led to believe that depression is a biochemical cause, but this new study shows that this belief is not evidence-based. It suggests, “says Moncliffe.

However, Sen warned against making decisions about treating depression based on this review.

“We usually do not make clinical decisions about treatment based on a molecular and biological understanding of what the treatment does. It is much based on the results of clinical trials,” Senator said. Said.

Scientists use rigorous clinical trials to see if treatment works and under what conditions it works for whom. Sen said these trials can produce useful results without a good understanding of how treatment works.

However, “I hope that a long-term understanding of biology will help develop better medicines and advance personalized treatments,” he added.

to date, Clinical trial Many SSRIs say, “They are reasonably effective and help some people.” “But we definitely need better medicines.”

For those who do not benefit from SSRIs, he said there are other potential treatments for depression, such as improved sleep routines, regular exercise, and stronger social connections. ..I’m using psychedelic drugs like these days Ketamine It is becoming more common as a potential option for people with depression.

“All of this has evidence of observational and clinical trials showing that they really help with depression,” he said.