Kava does not appear to increase serotonin levels in the brain. In fact, preclinical research shows that kavain, one of the main active compounds in kava, actually decreases serotonin outside of neurons. Kava’s well-known calming effects come primarily through a different system: enhancing the activity of GABA, the brain’s main inhibitory neurotransmitter. That said, kava does interact with the serotonin system in subtler ways, and those interactions matter, especially if you take medications that affect serotonin.
How Kava Affects the Serotonin System
Kava’s relationship with serotonin is more about modulation than boosting. Laboratory studies show that kavain reduces the amount of serotonin floating in the space between neurons. That’s roughly the opposite of what SSRIs and SNRIs do. Rather than flooding the system with more serotonin, kava appears to quiet serotonin signaling in certain areas.
Two specific kavalactones, kavain and dihydromethysticin, do interact with a particular serotonin receptor called 5-HT1A in the hippocampus, a brain region involved in mood and memory. They enhance the activity of compounds that target this receptor. The 5-HT1A receptor is the same one activated by the anti-anxiety medication buspirone, and stimulating it is generally associated with reduced anxiety. So while kava doesn’t raise serotonin levels overall, it may fine-tune how certain serotonin receptors respond.
GABA Is the Primary Target
The bulk of the evidence points to GABA as the main pathway behind kava’s calming and anxiety-reducing effects. Several kavalactones, including kavain, yangonin, and desmethoxyyangonin, bind to GABA-A and GABA-B receptors in a way similar to benzodiazepines, enhancing the brain’s natural “braking” signals. Neuroimaging research in people with generalized anxiety disorder has confirmed that kava influences GABA activity in brain regions tied to anxiety processing, particularly the dorsal anterior cingulate cortex.
Kava also promotes GABA production through an indirect route: by blocking calcium ion channels and inhibiting an enzyme called MAO-B, it shifts the balance away from excitatory signaling (glutamate) and toward inhibitory signaling (GABA). This multi-pronged effect on the GABA system is what gives kava its distinctive relaxing quality without the heavy sedation that comes with many pharmaceutical options.
Kava and MAO Enzymes
Your body uses two enzymes, MAO-A and MAO-B, to break down neurotransmitters after they’ve done their job. MAO-A primarily handles serotonin and norepinephrine. MAO-B handles other signaling molecules like phenylethylamine. This distinction matters because kava selectively inhibits MAO-B without significantly affecting MAO-A in living brain tissue.
In mouse studies, kava extract reduced MAO-B activity in the cortex and a region near the substantia nigra at doses as low as 10 mg/kg, while MAO-A activity in those same brain structures stayed unchanged. In lab-dish testing, kava did show some ability to reduce MAO-A activity, but only at the highest concentration tested (100 μg/mL), and this effect didn’t hold up consistently in living animals. The practical takeaway: kava is unlikely to raise serotonin levels through enzyme inhibition the way a true MAO-A inhibitor would.
Why It Still Matters for Serotonin Drugs
Even though kava doesn’t act as a straightforward serotonin booster, combining it with medications that do raise serotonin can be risky. A case report published in Cureus described a pediatric patient who developed prolonged serotonin syndrome, a potentially dangerous condition involving agitation, rapid heart rate, and muscle rigidity, after taking escalating doses of kava while transitioning between two antidepressants (duloxetine and venlafaxine, both SNRIs).
The suspected mechanism was not that kava flooded the system with serotonin on its own. Instead, kavalactones inhibit a liver enzyme called CYP2D6 that the body uses to clear certain antidepressants from the bloodstream. By slowing that clearance, kava effectively raised the concentration of the antidepressant, which then pushed serotonin levels dangerously high. The mild MAO inhibition from kava may have compounded the problem. No prior case reports of this specific interaction existed in the medical literature, and serotonin syndrome from kava alone has never been documented.
This is particularly relevant because many people turn to kava for anxiety while already taking prescription medications. The interaction is not about kava raising serotonin directly; it’s about kava changing how your body processes drugs that do.
How Kavalactones Reach the Brain
Five of the six major kavalactones (kavain, dihydrokavain, methysticin, desmethoxyyangonin, and yangonin) cross the blood-brain barrier in animal studies. This means they reach the central nervous system efficiently enough to produce real neurological effects, not just peripheral relaxation. That brain penetration is what makes kava’s GABA enhancement and serotonin receptor modulation possible, and it’s also why the drug interaction risks are real rather than theoretical.
Liver Safety Concerns
The FDA issued a consumer advisory in 2002 warning that kava-containing supplements may be associated with severe liver injury, including hepatitis, cirrhosis, and liver failure. Over 25 adverse event reports from other countries prompted the warning, and at least one case in the U.S. involved a previously healthy young woman who required a liver transplant. The risk appears to be rare but serious, and it’s worth keeping in mind if you’re considering regular use of kava supplements, particularly concentrated extract forms rather than traditional water-based preparations.