The fact that healthy people still get depression makes me skeptical of hypotheses like this. If it were as simple as taking probiotics, x and y supplements, and eating healthier, (and brushing teeth more), I think a lot more people would have beaten major depression by now.

Someone else in the thread suggested it's just exercise, sleep, and diet. Yet there are plenty of folks who do these things perfectly and still get depression.

Sure, I can understand your skepticism. The church was skeptical of Galileo when he made new claims about the nature of the earth as well, since it contradicted their own previous anecdotal perceptions and private ideology. If only we had developed tools like the scientific method to evaluate claims on the basis of evidence instead of personal skepticism -- then it could be possible to make some productive headway on the evaluation of whether or not an approach could be effective. Fortunately, these tools exist, so that someone who wanted to evaluate the claims behind the microbiota-inflammasome hypothesis of depression could click on a link to an overview of the scientific literature in support of the hypothesis, helpfully provided at the bottom of the comment [0], before posting a cursory dismissal on the basis of their personal skepticism.

The subject of the Quanta magazine article is a critical literature review which the article author describes as the "death knell for the serotonin hypothesis". The basis for your skepticism, "The fact that healthy people still get depression" could be addressed in the section of article where they explain how depression could be a catch-all umbrella term for the presentation of symptoms with a wide variety of causes, potentially including stress, genetic predisposition, tryptophan depletion, or chronic inflammation, among other possible causes like adverse childhood experiences or learned helplessness for example. Inflammation from periodontitis or gut dysbiosis can exist within the threshold of otherwise healthy people, as evidenced by the attenuation of symptoms in some sufferers of major depression by these interventions in the studies examined by the review I linked.

Maybe the reason a lot more people haven't beaten major depression through these interventions, as you suggest should have happened by now, is because when they go to the doctor, they get a script for an iatrogenic SSRI and a cognitive behavioral therapist and a kick out the door, instead of testing to see if they just need a root canal and some yogurt. And I protest your inclusion of magnesium orotate in the category of "x y supplements" as it is the target of specific studies which have examined its effectiveness in conjunction with probiotics in attenuating depression [1].

[0] https://sci-hub.st/https://pubmed.ncbi.nlm.nih.gov/30004130/

[1] https://link.springer.com/article/10.1007/s10787-017-0311-x

Lol Galileo over here. My comment was indeed a personal anecdote, nothing more. And I only wanted to establish that physiological factors like diet, exercise, and sleep, are not the ONLY contributors to major clinical depression. I'm pretty sure you agree? And you're saying there are MORE physiological factors (gut biome, gum health, etc), and... I don't disagree. The only purpose of my comment was to put to bed the assumption that some people have, which is that depression is purely, surface-level physiological (like just exercise/sleep/diet, not taking into account genetics, environment, stress, and all the other factors)