There seems to be an increasing number of non-academic articles, essays and books that are expressing the idea that the Serotonin hypothesis of depression is flawed. It seems like the drug industry just picked up this idea in the 70s and has been running with it (to the bank) ever since
Anecdotally, I have come to believe that SSRIs have a temporary mood-altering effect, possibly combined with a placebo effect that wears off over time - as your body adapts to the induced serotonin imbalance. The only answer from the medical profession? Increase the dose.
I saw this with my own mother. She went from being a mildly depressed retired housewife to suicidal within the space of 12 months. She started on low-dose SSRIs which seemed to work for a while before she regressed. Each time she started to feel depressed again she would be prescribed with an increased dosage. This pattern repeated until she was taking the maximum 'allowed' dosage, by this point she was delusional, paranoid and suffered terrifying, persecution-style hallucinations - perhaps not surprising seeing how much her brain chemistry must have been out of whack.
Sadly, I'm making these observations with hindsight, she took her own life in 2015. I wish I could share this article with my dad, if I knew it wouldn't break his heart. Both she and my father couldn't share with their children how gravely ill she was until it was too late. They both trusted their doctors implicitly. What they weren't prepared for was the fact that the theory that formed the basis of her treatment was, it seems, no more than guesswork supported only by publication bias, wishful thinking and greed.
Ironically, one of my first web development jobs, way back in 2000, was at a 'medical communications company' where I created an intranet site for GSK (IIRC) for use by their salespeople to shore up the claims of the effectiveness of Seroxat/Paxil and counter negative studies. So, I guess that makes me complicit in all this too.