Yet another study that gets at the “inflammation plays a big role in depression” hypothesis, and this time, it has to do with the release of histamine.
You already know this, but when we’re having an allergic response to anything, our immune system fights it by releasing histamine.
It’s a protective measure, and utterly vital for a properly functioning body, but sometimes it can start a chain reaction of crazy things (read here for that mechanism) that leads to allergies and other stuff under the hood that’s bad for us, as well.
It also can provoke high levels of inflammation throughout the body.
Chronic inflammation is a well-known risk factor for developing depression, and just about every other mental health disorder.
In fact, Dr. Charles Raison at Wisconsin wrote in 2018 (emphasis added): “Far from being specific to any one mental illness, or a sub-population within a mental illness, inflammation turned out to be a common denominator and likely risk factor for every manner of psychiatric disturbance, from schizophrenia to obsessive compulsive disorder, from mania to depression.”
That, for example, is just one of the reasons why researchers speculate that exercise, meditation, certain foods, and yes, antidepressants, can all help alleviate depressive symptoms — their effect on inflammation (among many other things).
(It’s important to note that, as Dr. Raison wrote in 2018, studies show that depression and other mental health challenges can’t entirely be explained by inflammation, and that we still can’t entirely explain them fully, scientifically, because they’re so enormously complex).
But…a recent study from researchers at Imperial College London and the University of South Carolina finds yet another way inflammation seems to affect depression — histamine release.
Here’s the very short version, and I would read Science Daily’s write-up for the longer, more comprehensive explanation.
Researchers used mice (of course) to test the idea that SSRI’s effect on serotonin (the neurotransmitter that helps regulate, among other things, our emotions) might be blunted by an interaction between neurotransmitters which include serotonin and histamine.
So they injected some mice with a toxin, provoking inflammation, and the control group mice got off mercifully with a placebo.
The mice who got the inflammatory toxin saw their serotonin levels immediately drop, whereas the control group’s serotonin level remained constant.
Now here’s the fascinating thing (if you haven’t stopped reading because you’re not into this type of thing).
The inflammatory injection was unable to cross the blood-brain barrier, meaning it could only affect serotonin another way.
And they found it was through histamine.
The inflammatory response triggered histamine in the brain, and that’s what seemed to lead to the reduction in serotonin levels.
I won’t bore you further, but I will.
Science Daily notes that the researchers gave the depressed, histamine flooded mice SSRI’s, but unfortunately, their levels of serotonin still didn’t rise to the level of the control group’s.
However, when the researchers gave them anti-histamines, suddenly, the inflammatory mice saw their serotonin levels rise back to the level of the control group’s.
In other words, the anti-histamines seemed to restore the feel-good neurotransmitter back to normal levels.
Now….. it’s really important to note that you shouldn’t reach for benadryl for your depression, because the anti-histamines researchers administered affected the whole body, and antihistamines for seasonal allergies only affect histamine’s effects on neurons.
Nevertheless, the potential impact is profound — both for future research and understanding depression itself.
The study authors urge more research into histamine’s role in depression, and of course, the possibility that a new drug could work on histamine in the brain to help fight depression (or at least make SSRI’s more effective).
The study’s lead author, Dr. Parastoo Hashemi, tells Science Daily:
“Inflammation could play a huge role in depression, and there is already strong evidence that patients with both depression and severe inflammation are the ones most likely not to respond to antidepressants.
“Our work shines a spotlight on histamine as a potential key player in depression. This, and its interactions with the ‘feel-good molecule’ serotonin, may thus be a crucial new avenue in improving serotonin-based treatments for depression.”
As a site dedicated to the message — Mental health is not reflection of spiritual health — this is yet another of scores of data points, reinforcing that.
(Of course, I can already hear deniers say, “The stress from an adulterous relationship could lead to chronic stress, inflammation, and therefore depression” and of course circumstances do play a role, but I suspect that’s not what’s going on with the vast majority of the millions of Christians and nonChristians who battle these diseases.)
There are a million more likely causes for the inflammation in our bodies. Completely amoral ones.
Like, did we eat deli meat for lunch today? I think there are more people, stopping for a quick inflammatory lunch, or working insanely hard to meet a stressful noon deadline, or operating on less than 8 hours of sleep than driving off for a lunchtime rendezvous at Red Roof Inn.
And that’s not even getting into genetics and the millions (hyperbolically) of other things involved, both known and unknown, in the development and persistence of mental health disorders.
P.S. The Atlantic had a fascinating piece on the mechanistic relationship between allergies and anxiety a few years ago, as well.
[Painting: Monet, Fields in Spring. Of course, histamine can be released by many things, but that field…..]
