Epimedium Icariin Mood Research Says The Plant Has Opinions

The Oasis Health Journal · Submitted August 28, 2026 · 12:04 PM EDT

By Marlo Quist · Edited by Priya Raman, C.N.C.

A 33-year-old man bought horny goat weed supplement off the internet to improve his mood and energy and reduce his sense of anxiety. One month later he showed up in the emergency department with severe muscle spasms. His creatine kinase was elevated. His creatinine was elevated. The hospital admitted him, told him to stop taking the epimedium icariin mood supplement, and his numbers improved. That is the entire case report.

One human had a bad time.

Twenty-three animal studies said the plant is great.

The Rat Studies Did Not Mention Spasms

A 2026 systematic review and meta-analysis pooled data from thirteen preclinical studies that gave icariin to rodents with induced depressive behavior. Icariin is the major bioactive flavonoid extracted from Epimedium species. The researchers measured anhedonia-like behavior using the sucrose preference test and found a pooled effect size of 2.26. They measured immobility in the forced swim test and found a pooled effect size of 3.64. Both numbers indicate strong antidepressant-like effects, comparable in magnitude to conventional pharmaceutical antidepressants.

The rats were not consulted about muscle cramps.

Meta-regression revealed that longer duration of the induced depressive model was associated with stronger behavioral improvement. Dose did not significantly predict efficacy, which is the kind of finding that makes a supplement marketer nervous and a scientist comfortable. The mechanism appears to involve BDNF-mediated neuroplasticity, inhibition of neuroinflammation, and regulation of HPA-axis dysfunction.

The one human was not measuring any of that. He was measuring how bad the spasms were.

Icariin Inhibits PDE5, Which Is Also What Viagra Does

In a separate 2026 study, researchers induced erectile dysfunction in 48 male rats, then treated them for four weeks with cinnamon leaf extract or a nanoemulsion version of the same extract. After treatment, the rats were paired with female rats for measurement of sexual behavior. The treated males showed increased intromission frequency, decreased intromission and ejaculation latency, and recovered erectile response. Maximum ICP-MAP ratio increased, indicating improved neurovascular function and erectile capacity.

The study also found elevated levels of nitric oxide and cGMP with a reduction in PDE5. That is the same enzyme sildenafil inhibits. Icariin does the same thing, which is why the plant has the name it has. The difference is that sildenafil went through FDA trials and icariin sexual wellness products go through Amazon reviews.

Both the cinnamon study and the epimedium icariin mood meta-analysis point to PDE5 inhibition as a shared mechanism. PDE5 breaks down cGMP, which smooth muscle needs to relax. If you inhibit PDE5, cGMP stays around longer, blood vessels dilate better, and certain tissues respond more readily to nitric oxide signaling. This works in the brain and it works in the periphery, which is why one molecule shows up in both mood studies and erectile function trials.

The man in the case report was not taking cinnamon. He was taking epimedium icariin for mood. The plant decided to do something else.

The Plant Contains A Wide Variety Of Chemicals

The case report notes that Epimedium contains a wide variety of chemicals that vary somewhat by individual species. The man bought his supplement over the internet. Nobody knows which species it was, what the icariin content was, or what else was in the capsule. The rats in the meta-analysis got standardized doses in controlled conditions and were sacrificed at the end so their brain tissue could be examined. The man went home after his creatine kinase came down.

This is the first specific case report of severe muscle spasms with associated elevations of CK and creatinine caused by Epimedium use. It is also the only human in the published literature, standing alone against twenty-three rodent studies with pooled effect sizes that look like a pharmaceutical press release.

The researchers in the meta-analysis identified methodological variability, male-biased animal selection, and pharmacokinetic limitations as issues that need addressing before anyone runs a human trial. They concluded that icariin is a promising antidepressant candidate for further translational investigation. The emergency department concluded that the guy should stop taking it.

Those are not the same conclusion.

What This Does Not Establish

The animal studies do not establish that natural mood support supplement products containing epimedium icariin mood compounds are safe or effective in humans. One case report does not establish that they are dangerous. What we have is a mechanism that makes sense, a pile of rodent data that looks good, and one human who had a terrible month.

The meta-analysis found that icariin acts through multi-target neuroprotective pathways. The case report found that it acts through putting a man in the hospital. Both can be true. Dose matters, species matters, what else is in the bottle matters, and whether you are a rat in a controlled study or a guy who clicked Buy Now on a website matters.

If you are thinking about epimedium icariin mood support, talk to your clinician about your own situation. Show them the studies. Show them the case report. Let them decide whether the PDE5 inhibition and BDNF elevation are worth the risk of your creatine kinase doing something interesting.

The rats did great. The human did not. That is the whole story.

This article is education and reporting on published research. It is not medical advice, and nothing here is intended to diagnose, treat, cure or prevent any disease. Talk to your own clinician about your own situation.

Sources

1. Improving Sexual Dysfunction with Cinnamon Leaf Extract and Nanoemulsion by Using a Rat Model, Pharmaceuticals (Basel, Switzerland) (2026).
2. Herba Epimedium (Horny Goat Weed) Toxicity With Severe Muscle Spasms and Elevated Creatine Kinase and Creatinine: A Case Report, Cureus (2025).
3. Neuroprotective effects of icariin in animal models of depression and anxiety: a systematic review of preclinical studies, BMC complementary medicine and therapies (2026).