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".

The creator of the Serotonin hypothesis admitted it was wrong, and he shifted to melatonin's precursor later in his career. The challange with any research in this area is Serotonin and Melatonin both affect biological functions by gradient activity not lock and key receptor models. This pair is how plants and animals respond to seasonal changes which vary year to year. Serotonin is the warm and light lide melatonin is for cool and or dark.

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.

https://pmc.ncbi.nlm.nih.gov/articles/PMC3779905/