Hormones:
Most people's androgen:estrogen balance (and levels) are absolutely off kilter, if they live a modern life (no exercise/only exercise is the gym, lack of sunlight, sitting down all day, living in a city, braindead birth control protocols with only estrogens, etc.).
Tuning that would be the most beneficial. And it would get to the root of the problem viz. fixing a mismatched upregulation/downregulate of neurotransmitter receptors (f.e. increasing sensitivity of GABA receptors, decreasing sensitivity of noradrenaline receptors, and so on) -- instead of just a simple and stupid "hur dur lets flood the synaptic cleft with serotonin/dopamine/catecholamines."
Barring that, there exist others that do not disrupt one's natural HPTA, and are more "targeted" towards neurons, rather than the whole body.
Peptides:
There are an assortment of peptides, but their main uses are specifically in gene expression/and cell signal tuning. They're hit or miss. A lot of woo-woo shit going on, and many people hype them up as a cure-all (because there's money to be made); when that's taken into account (and the lack of extensive research), you'll find an assortment of chemicals to play around with.
Russian synthetic adaptogens:
These are their own category of "adaptogens" popular in the Russian medical community (and seeing Western adoption). E.g. semax, bromantane, selank etc. They act as hormones/signaling molecules by changing the expressions of genes (leading to downstream changes of natural peptide levels, behavior of psychological/catecholamine systems, and so on).
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All of these, in my opinion and experience, are leagues better than the garbage that is peddled by the U.S's medical community -- because this actually changes shit on the genomic level, rather than fucking with the physical processes outright (ex. imagine the difference between cloud seeding to get more rainfall vs. diverting rivers, to fill aquifers. One of these is much more sustainable and has less side-effects).