Rosemary tea consumption results in anti-depressant-like behavior in mice
ncbi.nlm.nih.gov
ncbi.nlm.nih.gov
Do you have any references for that? From what I can tell, rosemary is native to the Mediterranean region and it is unlikely it was known in ancient India.
Press release: "rosemary extract discovered to be an effective anti-depressant."
Media release: "how a simple cup of tea could permanently cure your depression."
Social media (et al.): "feeling depressed? try this simple, secret tea Starbucks doesn't want you to know about that cures depression, boosts your IQ and prevents cancer!"
Cynicism aside, in an attempt to add something useful, there does seem to be some correlation between recall rate (memory) and rosemary extract, at least in certain disease states, with a parabolic dose curve (low = beneficial, high = detrimental).
There has been some chatter as to the specific MOA, however I think the presence of carnosic acid (a terpene present in rosemary) may be relevant--it seems to have PDE-inhibitory properties as well as a correlation with changes in cAMP/gAMP transduction.
Any effect is probably minor, however it's nonetheless intriguing. And if you care about the anecdotal/unproven cognitive benefits (ie, quite possibly placebo), many users online have reported benefits with PDE 4/5 inhibition (luteolin, artichoke extract ideally) combined with Forskolin (which you should always be careful about and know the source of because improper/unregulated extracts could be quite toxic).
http://www.ncbi.nlm.nih.gov/pubmed/22729658
Long story short, the study (6 refs) found dose-related hepatoxicity in mice, and also concluded Forskohlii's main mechanism of action was not directly responsible for the decreased function.
While not conclusive, it suggests to me that the industry surrounding it allows for a lot of "anonymous" stock to be packaged and sold (meaning, no heavy metal or contaminant controls).
Being an African plant potentially harvested w/o controls, and with supplement vendors looking for optimal prices, the incentives aren't tipped in the favor of transparency; an example of this actually happening was with Eurycoma Longfolia (tongkat ali) harvested from Malaysia that contained varying and dangerous levels of heavy metals. The context was similar.
Maybe the Hitchhiker's Guide was right!