Earlier quoted context omitted.
Agree. But sometimes there is no "root cause", the brain is still a mystery. If you had been depressed even when you knew there was nothing to worry about, you would see it differently, because then you deduce that the black cloud is produced within. Chemistry trumps psychology. Good enough chemistry enables cognitive treatments. But to fix the wrong chemistry you need chemistry.
The neurotransmitter model of mental illness is largely incorrect. It's much more complex than just "Depressives have less serotonin, therefore lets give a reuptake-inhibitor to keep serotonin in the brain".
My personal preference is to always suggest getting actual daylight on your retina for 20 min three times a week. Not through glasses, including eyeglasses, but can be through eyelids. That loads transferatin, as in transfer, this loads the enzyme that make serotonin. This then allows the body a better chance to make the intermediate between Serotionin and Melatonin, and is the one believed to help. But the patents have expired so it is like an orphan drug now.