> There are what, 500 different psycho-active chemicals in cannabis?

I think you're extrapolating from exaggerated factoids. There are only a small number of compounds in cannabis that exist at the intersection of:

- Present in high enough quantities to matter

- Not destroyed during smoking/vaping/processing

- Bioavailable enough to enter the bloodstream

- With the correct chemical structure to penetrate the blood-brain barrier

- Potent enough to elicit effects at the concentrations achieved in human consumption

There are not 500 compounds in cannabis that fit this criteria. The number is much smaller.

If there was some combination that achieved dramatic antidepressant effects where typical cannabis failed, don't you think someone would have noticed by now?

There's no reason to assume that some combination of 500 different variables exists to do something that we haven't observed yet. There are much more fruitful paths to research than endlessly researching every variation of cannabis for the sake of researching cannabis.