Benefits
Mood: animal research only, no human data
No human study cited on this page measured mood. This claim rests entirely on a 2013 rodent study in which flavonoids from Apocynum venetum leaves changed brain monoamine levels and produced antidepressant-like behaviour in animals. There are no depression scores from people, no placebo comparison in people, and no head-to-head comparison with an antidepressant medicine. Depression is a medical condition; if you are struggling with low mood, speak to a doctor rather than relying on a supplement.
Calming use is traditional, not tested here
None of the studies cited on this page measured anxiety or stress in people. The plant has a long history of use as a calming tea in China, and a review article describes that tradition, but traditional use is not the same as tested. The receptor effects described for hyperoside and isoquercitrin come from laboratory work, not from people taking the supplement.
Sleep: more deep sleep in one small brain-wave study
This is the one area with any human data. In a small 2015 study that recorded sleep with EEG, 50 mg of Apocynum venetum leaf extract taken on its own increased non-REM (deeper) sleep time by 7.6%. It did not shorten the time taken to fall asleep; GABA on its own did that, by about 5.3 minutes, and combining the two was no better than either alone. More non-REM time on a sleep trace is a laboratory measurement, not proof that people woke up feeling more rested, and a single small study is a thin basis for a sleep claim.
Mechanism of action
What the flavonoids do in the lab, and what that does not prove
In laboratory and animal work, hyperoside and isoquercitrin appear to affect serotonin signalling, and a rodent study reported changes in brain serotonin, dopamine and noradrenaline. That is a plausible idea about how the extract might work, not something measured in people. It does not make the extract equivalent to fluoxetine, sertraline or any other prescription medicine, and no human study cited here measured mood, anxiety or brain chemistry.
Clinical trials
A small human study that recorded sleep with EEG. It compared GABA on its own, Apocynum venetum leaf extract on its own at 50 mg, and the two combined.
A small group of adults. Sleep was measured on a brain-wave recording; mood and anxiety were not assessed.
The leaf extract alone at 50 mg increased non-REM (deeper) sleep time by 7.6%. GABA alone shortened the time to fall asleep by 5.3 minutes. The combination gave 4.3 minutes and 5.1% more non-REM sleep, so it was not better than either ingredient on its own. No depression, anxiety or mood outcome was measured, and the study reports sleep-trace measurements rather than how rested people said they felt. It is a single small study.