The common belief that depression is tied to serotonin levels in the brain is a myth, argues British psychiatrist David Healy in a controversial editorial published Wednesday in the medical journal BMJ.
Healy, who is a professor of psychiatry at the Hergest psychiatric unit in North Wales, argues that low levels of serotonin have nothing to do with depression. He suggested that since the 1980s, people have been wrongly prescribed SSRI (selective serotonin reuptake inhibitor) drugs such as Prozac because of Big Pharma's "marketing of a myth." But SSRIs are widely considered helpful to treat depression, and are also thought to be safer than older "tricyclic" drugs.
Healy wrote that the SSRI group of drugs came into vogue in the late 1980s, despite being mooted earlier in the 1960s. The resurgence in their popularity, he said, was due to rising concerns about dependence on tranquilizers—drugs such as Valium and Xanax—in the early 1980s.
I reached out to the Royal College of Psychiatrists, and although no one was available for comment, they sent me over a statement, which had been prepared as a response to Healy's editorial. In the statement, Professor Sr Simon Wessely, President of the Royal College of Psychiatrists said: "That antidepressants are helpful in depression, together with psychological treatments, is established. How they do this is not—most researchers have long since moved on from the old serotonin model. Most important of all, the newer drugs—the SSRIs, are safer if taken in overdose than the older tricyclics."
Serotonin is involved in virtually every aspect of the human body. It can be found in the gut, the bloodstream, the bones, and the muscles. Healy argues that as it's one of the most primitive neurotransmitters, once interfered with, people risked other things going wrong in their bodies. "These drugs act on your muscles and on your bones, so that increases the risk of muscle problems or stroke," he told me.
Healy said that SSRIs' use in alleviating depression was initially based on a series of assumptions. "Because people thought these drugs (SSRIs) act on a few different systems, including the serotonin system, they thought that something was wrong with the serotonin system of people who were depressed," he said.
"The marketing departments of companies trying to sell these drugs came up with the idea that what the drugs (SSRIs) do is correct lowered serotonin," Healy told me. "The was the kind of idea that worked tremendously well with a lot of doctors, and patients. It seemed to provide a reason to give the pill but it was completely wrong. It was simply a marketing idea."
In 2005, a study published by Jeffrey R Lacasse and Jonathan Leo explored the lack of evidence suggesting that serotonin levels were linked to depression. The researchers argued that while SSRI advertising has "expanded the antidepressant market," there is little scientific evidence to prove the link between serotonin and depression. In another study conducted in 2014 by researchers at the Wayne State University School of Medicine, it was found that "mice lacking the ability to make serotonin in their brains did not show depression-like symptoms."
While according to Healy, the pharmaceutical industry has churned out this myth to generate profits, he said that most at fault were the doctors and psychiatrists who had been prescribing the SSRIs to patients since the 1980s.
"Doctors get trained in physiology and pharmacology, but the one thing they should be trained about is in how companies market to them," said Healy. "In order for you to get the drugs, you only need to go to the doctor, so companies only need to market to doctors. People like me, doctors, haven't asked the pharmaceutical companies tough questions."
While Healy asserted that SSRIs do not work on severely depressed people, John H. Krystal MD, a professor in Psychiatry at the Yale School of Medicine, told me over email that "the response to SSRI antidepressants appears to be different for every individual, as opposed to being non-effective for all." Krystal also said that the role of serotonin on the cause of depression still was unclear, and supported the view put forward by Wessely that psychiatry had abandoned the "low serotonin" hypotheses as the cause for depression long ago.
In a study conducted in 2011, Krystal reanalysed data from seven clinical trials involving 2,515 patients treated with SRI antidepressants or placebo. He told me that "the majority of patients (over 75 percent) showed a superior response to patients treated with placebo. However, nearly one quarter of patients treated with SRIs showed a poorer response than patients treated with placebo." This finding, said Krystal, raised the "critical issue of whether there are ways to identify those patients who would seem to be better off avoiding SRIs and to divert these individuals to other treatments for their depression."
Over the phone, Healy stressed that the main danger lay in Big Pharma overhyping SSRIs as having more benefits than side effects, and for doctors and psychiatrists not to question this. Similar critiques of Big Pharma were also voiced in 2013 by psychotherapist James Davies, who argued on Channel 4's Fact Check programme that "the so-called advantages of these medicines have been oversold and overplayed by the pharmaceutical industry and by members of the medical profession who have been recruited by the industry to sell up the advantages to other doctors and to their patients."
Exactly how SSRIs work is still unknown. However, on concluding his statement, Wessely advised that people should not change their current medication.