I'd be surprised if depression turns out to have a singular cause or mechanism. It's simply a group of symptoms that often occur together.
The way we currently speak about depression is as if we labeled the combination of fever, coughing and sweating as "the hots". You'd expect to quickly find remedies like "Tylenol reduces symptoms of the hots", followed a decade later by papers "the hots not caused by Tylenol imbalance", with people contradicting it with "I can't live without Tylenol, it's as important to me as insulin for a diabetic". Both can be right, Tylenol just happens to reduce the symptoms without doing anything about the cause. Any actual cure you find would appear to only work for a small portion of patients. Not because it's ineffective, but because "the hots" isn't one distinct illness, but a symptom of many possible conditions, and you have to use different strategies to cure each one.
Actually, I think you might be better looking elsewhere for help with depression. In my own experience, and that of other people I know, psychological factors have always been the main cause of depression, and resolving them results in curing the depression. The problem is that it isn't always easy to identify the factors causing the depression.
As for the science: we do know that both psychological stressors and infections both cause inflammation. Stress results in activation of the HPA axis and sympathetic nervous system, which screws up the immune system in various ways (including inflammation). Conversely, having a severe infection can make you feel depressed.
It's really just a theory that inflammation causes depression. I think it's more likely that it's a result of cortisol and/or neurotransmitters (i.e. too much brain activity). Cortisol seems a more likely candidate for being central to depression in my opinion.
The science here seems to be based on a desire to have a physical rather than a psychological cause for depression. Michael Maes has a history of that (see his CFS publications).
Mood disorders might have underlying causes, but the diagnosis and definition is entirely based on the symptoms. Comparing it to having a cold is a bit misleading. It's more like having a couch, or itchy throat, that may be caused by cold, but it's not the diagnosis you'd get.
Could you cure a cough with couch syrup? Could you cure a sore throat with pain killers?
Antidepressants makes the basis for a depression diagnosis go away for some of those who are treated. Having no measurable level of depression is probably the closest we will ever get to a cure of depression at large.
If the depression is caused by something specific, say a vitamin deficiency, that underlying issue would of course not be treated by SSRI. But we don't know enough to say that there always is something specific causing the symptoms. What if the issue is actually a serotonin deficiency? Just like some people naturally produce to little vitamin D and have to take supplements.
What if not all DNA sequences lead to a happy life? There's nothing in evolution that enforces that all offspring has to be happy for survival to happen.
That's an interesting post, though I do think the cause you've suggested is only a subset of possible causes of depression.
Depression is an illness that is defined by its symptoms. The causes are diverse and can be deeply personal. This is unlike most other illnesses, where there is a much smaller set of possible causes for a given set of symptoms. For some illnesses the causes are unavoidable, I can't do anything to prevent the catching a cold, I have to step outside and interact with the world where the virus lives. For others causes can be addressed, for example, I experience stomach pains after drinking milk so I stop drinking it.
The current state of mental health care is in terrible shape. Doctors do not have the time to provide psychiatric advice but they do have just about enough time to sign off SSRI prescriptions. Your pills may help you get through the day a bit easier but if you do not address the cause of your illness your symptoms will eventually surface again. There are cases where perhaps the cause is completely due to a chemical imbalance but from all I've read about depression, this seems rare. Most of the time the suffer needs help addressing the root cause of their depression. Sometimes it's learned helpnessness which needs a change in our mental model, sometimes its about quitting destructive habits/addictions or sometimes we understand reality completely and just need to change our behaviors to become satisfied with life.
The root cause of depression is chemical not psychological. It's a natural process and everybody gets depressed sometimes. If you get depressed, you can fix it by behaving like a normal person following normal person schedules and doing normal person things like sports and eating good food. Well... unless you can't because you're really sick and not just depressed. Those with CFS have tried following the recipy of getting cured and failed. Time and time again. Sometimes they succeed for no good reason but mostly after some time of being normal it all falls apart again.
Depression and anxiety may as well be the cough and fever of the mental health world. We can certainly treat cough and fever symptoms but that is quite different from treating the underlying condition.
I think the big problem is we probably have a lot of recent societal/cultural changes which at least contribute to depression and anxiety, but are very hard to detect because of near universal adoption + too many confounding variables when examining holdout populations. Thinking of things like diet (and trace chemicals, pesticides), sleep habits, screen usage (internet, social media, porn, passive media, games), caffeine, etc. Somewhere in those areas, IMO, likely lie very large causal contributors to all of the reportedly increasing mental health problems we are seeing.
I can also speak from personal experience that I had very debilitating depression/anxiety as an adolescent which has since greatly leveled off but not quite cleared. While I could likely still be diagnosed with depression now, to me the two states comparing now vs then are so wildly, qualitatively different that I am convinced they represent different underlying pathologies. What I have now feels more like the same thing that most other malcontents seem to have.
What this suggests to me is that what we diagnose as "depression" has multiple causes, and current antidepressants are fairly effective at treating at least one of them.
It's as if we had a single category for "breathing trouble" and consistently treated it with antibiotics. Sometimes it's bacterial pneumonia and that works very well. Often it's emphysema or lung cancer, and antibiotics don't help.
I'm learning more and more about this by talking to my wife's doctors, and you're right in the sense that there are some forms of depression that can be cured, but sadly not all.
I'm broadly generalizing here, but depression caused by a physical condition (e.g. an autoimmune deficiency) can typically be cured by attacking the underlying cause, but depression caused by a psychiatric condition is much harder to "cure" in the traditional sense and instead can be managed via modern pharmaceuticals. Now, those drugs come with some strings attached, but if they help a patient get out of the bed and function in the morning (as they do with my wife) then that's a net positive, but we're realistic about the fact this is likely a life-long battle that will require constant work to stay on top of.
The fundamental problem is how cripplingly little we understand about neurobiology. "Depression" is a label given for a common cluster of symptoms, not a single disease originating from a few well-understood causes. We aren't able to objectively test for or treat it the way we can X-ray a broken bone and set it or swab a throat for strep and prescribe antibiotics. There are no methods that are guaranteed to help the vast majority of sufferers and no clear understood root causes. All we can do is ask for the patient to report their subjective experiences and try to tick some boxes in the DSM, find a label that describes at least N/N+M of their symptoms, and then work through an associated checklist of wildly different methods of "treatment" that reduce symptoms in some, but not all (or even a majority, AFAIK) of patients.
I personally think that many (if not most) of the mental illnesses listed in the DSM will eventually be understood to be multiple completely unrelated root conditions that all manifest similar symptoms, each with different methods of treatment. Unfortunately research initiatives tend to be shackled to the DSM's set of superficial symptom groupings in order to get funding, so a deeper understanding of them is probably a long time coming.
The way I understand it, depression is a disease like the flu, or whatever thing that made you feel like shit.
With the flu, you can't just wish the virus away, and you will feel like shit until your immune system and whatever treatment you received has done its job and your body has recovered. I tend to think it is the same with depression, your lungs may not be under attack, but you are still sick and it has to be treated like a real disease, possibly with medication. And I wouldn't be surprised if many depressions could be explained by conventional pathogens like viruses and bacteria.
There are multiple kinds of depression, and because of that there is never going to be a one pill cure all, until we start studying different kinds of depression.
However with that being said, there is a correlation between some depression and stomach inflammation. For many emotional feelings are tied to the stomach. Something as small as a stomach ache can sometimes leave a person in a cruddy mood. I wonder if this is why anti-inflammatories help.
(On a more cheerful note, anti-inflammatories got spell checked to anti-flamethrowers on my computer.)
So I agree that there's been a move away from "low seretonin == depression" and the model that depression is due to low seretonin (if it was even in favour), is giving way to "it's much more complex. We don't understand too well". [1]
And, there is an argument that is made that such drugs aren't effective anyway (or no more than placebo).
However, I think that's an over simplification [2]. And I don't necessarily accept the contention that SSRIs / SNRIs and others just treat symptoms.
This goes back to what I was saying earlier, that what works for person X may not work for person Y, not because the treatment isn't effective by itself, but because the etiologies may be different. All the way from a single SNP (single nucleotide polymorphism)) introducing a subtle amino acid substitution in a receptor on the cell surface to the cause being due to a vitamin deficiency (B-complex, for instance, or vit D, as another comment mentioned, or low Mg levels!) to psychological trauma. There are so many reasons that can lead to depression & anxiety.
It's like fever. Some fevers can be treated with Tylenol. Others will need quinine, and Tylenol in such a case would be ineffective.
What it also means is that we need to find better therapeutic targets in addition to seretonin / dopamine receptors, etc., and maybe move to a combinatorial drug approach once the targets are identified & validated. (like is used in oncology).
So please do not dismiss drugs. Or therapy. Or CBT. Or lifestyle changes (diet, exercise). Environmental changes (job, social circle). It could be any of these that can help someone deal with, navigate through and resolve depression. And it can be frustrating to try and narrow down among these. But that's the nature of the beast :/.
But in most cases depression is a natural response to the difficulties of life. It's like when your immune system triggers an inflammatory response to infection. It's painful but natural; and the cause is external. Willpower can't cure depression any more than it can reduce inflammation. But in the case of mental illness, the external agent is socioeconomic hardship, family dysfunction, loss of a loved one, etc.
There are too many different factors that affect depression. Genetic susceptibility, time of year, relationships, various psychological factors, social factors, etc. Meds will not cure depression, but they will alleviate the symptoms while you work on addressing some of the factors that cause it.
Think of it like Ibuprofen. It's there to help you manage pain, but it won't fix things.
You would be quite wrong. We do know some bits about the effects of serotonin in the body, though I would be amazed if we really understood the whole story.
But more than that, we have no idea what depression actually is, and that goes for any other psychiatric disease unrelated to direct brain damage. It would probably be more correct to call these syndromes rather than diseases, as we do not know the mechanisms causing the disease enough to even be sure if 'depression' is a meaningful diagnosis (in the sense that coughing is not a diagnosis).
We also don't have proper neurological studies of emotional illnesses - there are basically no comparative neurological studies of people diagnosed with depression versus people showing similar symptoms who are expected to quickly recover (for example, people grieving for a lost one). We don't know whether the brain chemistry changes we see in depression are the cause of the disease, or just the way 'sadness'/'lack of motivation' looks like neuro-chemically.
The way we currently speak about depression is as if we labeled the combination of fever, coughing and sweating as "the hots". You'd expect to quickly find remedies like "Tylenol reduces symptoms of the hots", followed a decade later by papers "the hots not caused by Tylenol imbalance", with people contradicting it with "I can't live without Tylenol, it's as important to me as insulin for a diabetic". Both can be right, Tylenol just happens to reduce the symptoms without doing anything about the cause. Any actual cure you find would appear to only work for a small portion of patients. Not because it's ineffective, but because "the hots" isn't one distinct illness, but a symptom of many possible conditions, and you have to use different strategies to cure each one.
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