Other names Origanum Vulgare Leaf Extract, Oregano Oil, Oregano Essential Oil
Anecdotal evidence and animal studies suggest oregano might alter brain function to improve mood and possibly cognition. But how effective is oregano actually as a nootropic? Read on to find out what the scientific evidence says.
Read about the effects of Oregano in relation to the amount of evidence we've found
Potential mood benefits of oregano
Brain tissue concentrations of both tyramine and dopamine were increased in ants that received an oregano extract.  The changes in tyramine and dopamine levels likely had an impact on the locomotor activity as well as the aggressiveness of the ants, but this research cannot be easily used as a basis for reasoning about how oregano extracts might influence human work and social behavior. But it does indicate that oregano extracts have the potential to influence brain monoamine levels, a phenomenon evidenced by several other animal studies.  In mice, oregano extracts were found "... to inhibit the reuptake and degradation of the monoamine neurotransmitters in a dose-dependent manner ..." and also resulted in "... an elevation of extracellular serotonin levels in the brain." These neurochemical effects of oregano extracts, if present in humans, suggest that using supplements based on this herb might be an effective cognitive intervention and might also in fact enhance mood.
Another study found that carvacrol which is one of the main active ingredients in oregano had the following effects in rats:
"Carvacrol, administered for seven consecutive days (12.5 mg/kg p.o.), was able to increase dopamine and serotonin levels in the prefrontal cortex and hippocampus. When single doses were used (150 and 450 mg/kg p.o.), dopamine content was increased in the prefrontal cortex at both dose levels. On the contrary, a significant dopamine reduction in hippocampus of animals treated with 450 mg/kg of carvacrol was found. Acute carvacrol administration only significantly reduced serotonin content in either the prefrontal cortex or in the hippocampus at the highest dose. Moreover, acute carvacrol was ineffective in producing changes in the forced swimming test. Our data suggest that carvacrol is a brain-active molecule that clearly influences neuronal activity through modulation of neurotransmitters. If regularly ingested in low concentrations, it might determine feelings of well-being and could possibly have positive reinforcer effects." 
The fact that oregano extracts have effects on key neurotransmitters are a reason to be cautious with high doses of such supplements since increased levels of monoamines (e.g. dopamine) have also been linked to mental disorders such as schizophrenia in humans. So while evidence from these animal studies does suggest oregano extracts can have psychological effects in humans if dosed appropriately, it is not certain that these effects are desirable. This is why researchers also measured the behavioral effects of oregano extracts in mice.  The findings from one such experiment suggest that the effects of oregano extracts on mice behavior are in fact beneficial and similar to that seen from effective antidepressants when given to humans. 
Yet another study on the antidepressant effects of oregano (essential oil) in rats found that oregano could protect animals from depressive symptoms in an animal model. Oregano did not reverse all of the neurochemical effects of chronic unpredictable stress but still protected the rats from depressive behavior when in a depression-inducing context. 
Oregano contains many antioxidant compounds, including apigenin and luteolin, as well as flavanols such as quercetin.  It is likely that the doses of oregano commonly used as a spice to improve the taste of various dishes aren't optimized for cognitive and mood-related effects.
Potential antioxidant benefits of oregano
One of the active ingredients in oregano essential oils is carvacrol, a phenolic monoterpenoid compound.  It has been found to exert antioxidant effects in animal studies. Oregano extracts have been found to reduce free radicals in at least one in vitro study, in which it acted synergistically with ajowan extracts (from a natural herb) to reduce oxidative stress biomarkers. 
In one study on rats, a neurotoxin that adversely affected oxidative stress and lipid peroxidation in brain tissue and impaired psychological, motor and cognitive functions was not as toxic when carvacrol was also administered to the rats as when carvacrol was not given to the rats.  When carvacrol was administered to these rats together with the neurotoxin it "... ameliorated most of the undesirable effects ...". However, it is very hard if not impossible to know first how generalizable these findings are to humans and second how much carvacrol is in the products available for consumers of nootropics (this info is usually not given by companies that sell nootropics).
Potential cognitive benefits of oregano products
In one study in rats with impaired glucose metabolism carvacrol, which is present in oregano, promoted biochemical states associated with healthy cognitive functioning and preserved cognitive functions in the context of experimentally induced diabetes. 
The legality and side effects of Oregano
Frequently asked questions about Oregano
Studies conducted on the effects of Oregano in healthy humans
Last updated Saturday, June 10, 2023