Comment by Liquix

can vouch for a diet high in fatty fish along with supplementation of D3 + cofactors (K2, A, magnesium, zinc, copper, boron). sample size of one but noticeably improves mood and energy levels.

recent evidence [0] suggests there's not much of a link between serotonin and depression, and therefore the effects of SSRIs are either placebo or an as of yet unexplained mechanism of action. IMHO it seems much more likely that modern lifestyles (excessive screen time, poor diet, lack of socialization, no connection to nature, no spirituality, etc) have more of an effect than serotonin levels.

[0] https://pubmed.ncbi.nlm.nih.gov/35854107/