A look at the evidence for stress and anxiety supplements

Kava

In the best and largest study (partly funded by a kava supplement maker), researchers randomly assigned 171 adults with generalized anxiety to take a daily placebo or 240 mg of kavalactones (kava’s active ingredient).

After 16 weeks, anxiety scores dropped similarly in both groups. But those taking kava reported poorer memory and muscle tremors more often than the placebo takers.

What’s more, liver enzymes increased in the kava group, though no kava takers suffered acute liver injury (a known risk of kava).

GABA

In one of the few studies (none of them rigorous), 63 young Japanese adults took a placebo or 100 mg of GABA on separate days before performing mentally taxing tasks.

According to questionnaires filled out by the volunteers, feelings of “vigor” dropped less when they took GABA than when they took the placebo.

But the authors didn’t report the questionnaire’s results for anxiety or depression. Why not?

Ashwagandha

In one study, 58 adults with “moderate” stress were randomly assigned to take 250 mg of ashwagandha, 600 mg of ashwagandha, or a placebo every day.

After 8 weeks, stress fell by a modest 8 to 9 points (on a scale of 0 to 40) in the ashwagandha takers versus 6 points in the placebo takers.

But in another (company-funded) study of 57 adults who also had “moderate” stress levels, those who took 225 mg or 400 mg of ashwagandha every day for 30 days reported no less stress or anxiety than placebo takers.

L-theanine

In a small study co-authored by supplement company employees, 12 young men reported lower levels of stress and anxiety when they took 200 mg of L-theanine rather than a placebo before taking a challenging math test.

But even if those results are confirmed by larger studies, it doesn’t mean that L-theanine can help people with anxiety disorder.

Australian researchers (who were partially funded by a supplement maker) randomly assigned 46 adults with generalized anxiety to take either 450 mg of L-theanine or a placebo every day. (After a month, the researchers bumped up the L-theanine to 900 mg a day for those whose symptoms hadn’t improved.) After two months, anxiety scores dropped similarly in both groups.

CBD

In several trials, high doses of CBD (cannabidiol) lowered anxiety caused by a stressful situation like public speaking.

But results are inconsistent.

In one better-designed study, for example, researchers randomly assigned 32 adults with high levels of paranoia (but no psychosis) to take 600 milligrams of CBD or a placebo. (The senior author had ties to the CBD industry.)

Two hours later, the volunteers were immersed in a stress-inducing virtual reality session that made them anxious and raised their heart rate and blood pressure. Those who were given CBD fared no better than the placebo takers.

Research on lower doses isn’t very encouraging, either. (Many CBD supplements, gummies, and oils have no more than 30 mg of cannabidiol per dose.)

In the only study using low-dose CBD—it was funded by a CBD company—healthy adults with overweight or obesity who took 15 mg of CBD every day for six weeks reported no greater improvement in measures of well-being like stress, sleep quality, relaxation, or mental clarity than those who took a placebo.

But that hasn’t stopped companies like Charlotte’s Web from marketing its 10 mg CBD gummies to “ease normal anxiety” and “manage everyday stressors.”

Low doses of CBD aren’t likely to help people with high levels of stress or anxiety, either, though they haven’t been tested.