The Flawed “Study” that Says Serotonin Doesn’t Cause Depression

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Another day, another load of garbage in the mainstream media claiming that a study proves antidepressants don’t work. I never should have told that disembodied monkey hand I wanted to make videos about anything besides COVID misinformation.

It’s been three whole months since I made a video about sketchy mainstream media reporting on antidepressants so I will once again start this video by saying that if you are taking antidepressants or other pharmaceuticals to aid your mental health under the guidance of a doctor, absolutely do NOT stop taking them without talking to that doctor first and following their advice. I am NOT a doctor, and nothing I’m about to say should supersede what your doctor says.

Also, if you are feeling depressed or suicidal, please speak to your doctor about it. If you don’t have access to a doctor due to a lack of insurance or money, there are community-based health centers that may be able to help you on a sliding scale. Or, if you’re in the US you can get help 24/7 from the National Alliance on Mental Health by texting “NAMI” to 741741.

Okay, let’s jump right in with the good ol’ Daily Mail, and please note that everything I’m about to read to you is wrong: “Have millions been taking antidepressants with harmful side-effects for decades – when there’s no scientific evidence they do what they claim? Some experts have suspected it for years. Now patients have been left reeling by a groundbreaking study.”

“New research shows the theory justifying antidepressants is just a myth

The research confirms what some medical professionals have suspected

Depression being a chemical imbalance has been proven to be unfounded”

To repeat, everything I just read to you is wrong. So incredibly, stupidly, infuriatingly wrong. “There’s no scientific evidence (antidepressants) do what they claim?” Wrong. There are HUNDREDS of randomized controlled trials that show that antidepressants help people with depression at a higher rate compared to placebo. There is no “new research” that rebuts this. None.

Here’s the “new research” that this piss-soaked rag is referring to: “The serotonin theory of depression: a systematic umbrella review of the evidence,” published last week in Molecular Psychology. As the title may give away, this is not a new study but a systematic review of previous research. As I always warn when it comes to systematic reviews and meta-analyses, they can go in two very different directions: on the one hand, they can provide a necessary overview of the research on a particular subject by looking at various studies over a number of years, but on the other hand they can be misleading if the authors cherry pick only the studies that show what they want them to show.

But before we even get to that, the title should also give away the fact that this was NOT a review to determine whether or not antidepressants work (which, again, they do). This was a review to determine HOW antidepressants work. Because in all fields of science, researchers accept that sometimes we know that something works but we’re not yet sure why, like when James Lind performed a randomized controlled trial that found that citrus fruit cured scurvy in 1753. Vitamin C wasn’t discovered for another 150 years.

The brain is a complicated lump of meat, so it makes sense that how it works remains a big question. In the late 1980s, doctors found that depressed patients could be helped by giving them fluoxetine, more commonly known as Prozac, which is a selective serotonin reuptake inhibitor, or SSRI. SSRIs, to put it very simply, change the way your brain processes serotonin, causing serotonin to stay for a longer period of time in your synapses.

This led some researchers to think, quite understandably, that maybe people are depressed because they need more serotonin. That hypothesis got popular in the years that followed the introduction of Prozac and it certainly became popular amongst the general public, but serious researchers knew that it was always going to be more complicated than that. They already knew that depression has many causes: yes, there’s an imbalance of chemicals in the brain which might include serotonin, but there’s also depression that comes from bad life events, or from physical ailments. Just because it helps a person when you adjust their serotonin levels, doesn’t mean the problem was the serotonin levels. I’ve heard several doctors recently explain it like this: taking Advil may help your headache but it doesn’t mean that your headache was caused by a lack of Advil in the brain.

So experts haven’t seriously thought that depression is simply JUST a lack of serotonin for quite some time. That said, science isn’t just about publishing exciting and novel new theories–the backbone of science is definitively disproving what we suspect isn’t true. So it may be worthwhile to publish an overview of previous studies on serotonin. You may pick up on the fact that I’m hedging a little here: It MAY be worthwhile? Well, to truly cross out “serotonin imbalance” we’d want, for a start, to narrow down the data to just those people who are depressed due to a suspected chemical imbalance, and exclude those who have other possible causes. But there are other issues, as well.

Asia Murphy, an excellent wildlife scientist and photographer worth following on Twitter, posted a link to a few experts responding to this systematic review, and they aren’t exactly impressed with it. I found a few of their thoughts really interesting: several of them point out the possibility of cherry picking, but a real eye-opener for me came from Professor David Nutt at Imperial College London, who wrote:

“This meta review covers much of the work done over the past 50 years to explore the relationship of the serotonin system to depression. Unfortunately, all of these variables are indirect measures of serotonin function or even worse (as in the case if the gene-linkage studies) merely proxies for serotonin activity. It is only recently that we have developed the technology to measure serotonin release in the living human brain and in the first study of this type (currently under review) we did find decreased serotonin release capacity in people with depression. So, to dismiss the serotonin hypothesis of depression at this point is premature.”

That’s actually really interesting and I had no idea that researchers have found a way to directly measure serotonin in a living person. Cool! 

So to recap, this review is NOT a new study, it does NOT comment on the effectiveness of antidepressants, and it doesn’t even really seem to provide solid evidence to reject the idea that some depressed people suffer from a serotonin imbalance. As always, you can ignore the Daily Mail and you can even skip the less shitty mainstream media takes about this review. And please, don’t stop taking your psych meds based on anything other than your doctor’s recommendation.

Rebecca Watson

Rebecca is a writer, speaker, YouTube personality, and unrepentant science nerd. In addition to founding and continuing to run Skepchick, she hosts Quiz-o-Tron, a monthly science-themed quiz show and podcast that pits comedians against nerds. There is an asteroid named in her honor. Twitter @rebeccawatson Mastodon Instagram @actuallyrebeccawatson TikTok @actuallyrebeccawatson YouTube @rebeccawatson BlueSky

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