Kanna (sceletium tortuosum) is an herb that has traditionally been taken for its calming effect. Growing studies show its ability to help relieve anxiety in stressful situations.
It is also being studied for its anti-depressant effect.
Kanna is native to South Africa and has customarily been chewed for its mood-enhancing properties and for coping. While more evidence is needed before recommending kanna, its main role of reducing anxiety caused by stressful situations appears to be promising.
It is believed that kanna’s mechanism of action is attributed in part to its ability to influence the amygdala of the brain (a brain region that has a central role in emotion and behavior).
Kanna contains several alkaloids, with mesembrine and mesembrenone believed to be the major ones identified. These alkaloids have psychoactive properties, but are not known to be hallucinogenic or habit forming (1).
The alkaline mesembrine acts as a serotonin reuptake inhibitor that prevents the absorption of this hormone, which leads to an increase in serotonin levels in the brain. Low levels of serotonin are linked to depression.
Mesembrenone acts as both a serotonin reuptake inhibitor and a phosphodiesterase 4 (PDE4) inhibitor, which is associated with improved cognition, anti-inflammatory effects and neuroprotective properties.
Kanna helps reduce anxiety. In 2011, researchers evaluated kanna’s effect on psychological stress using a rat study. Male rats were administered 5 or 20 mg/kg/day of sceletium tortuosum extract or placebo for 17 days.
Fifty percent of rats were exposed to repeated restraint stress lasting one hour for the last three days of treatment. Rat behavioral changes in response to stress were assessed using the elevated plus maze on the last day of restraint, immediately after the restraint session.
It was noted that supplementation reduced anxiety and attenuated the increase in corticosterone (a stress hormone); the lower dose appeared to be slightly more effective than the higher dose, while the higher dose seemed better at preventing immune system-related abnormalities (assessed by serum biomarkers 2).
In another study, kanna was found to be effective in reducing anxiety attributed to cognitive stress. Zembrin is a brand name of a standardized extract of kanna that has been used in many studies to assess this herb’s effects.
In a double-blind, placebo-controlled, cross-over design, 16 healthy participants were scanned during performance in a perceptual-load and an emotion-matching task.
Supplementation of kanna reduced the reactivity of the amygdala in response to the test, thereby reducing stress compared to placebo (3).
Kanna may help treat depression. Due to the presence of the alkaloid mesembrine in kanna that has been shown to act as a serotonin reuptake inhibitor (many commonly prescribed antidepressant medications inhibit the reuptake of serotonin), researcher set out to evaluate its effect on depression.
In a study of rats, sceletium tortuosum supplementation had some antidepressant properties (as assessed by a forced swim test) but also produced a loss of voluntary muscle control (ataxia).
In a test assessing kanna’s neurocognitive effects in non-depressed participants, researchers found that in addition to improving cognitive set flexibility and executive function, it led to positive changes in mood and sleep.
Supplementation was also found to be well tolerated (4).
According to a review published in the Journal of Ethnopharmacology, several human clinical case reports demonstrate kanna’s ability to help treat those diagnosed with depression.
In one case, the patient was suffering from severe depression for four months, with reports of poor appetite, weight loss, insomnia, decreased energy and anxiety. The patient was given a daily dose of 50mg of sceletium and reported an improvement in mood, generalized anxiety and insomnia.
In a second case, a patient with major depressive disorder experienced similar improvements. The patient took 50 mg twice a day (in the morning and at lunchtime). On the first day of treatment the patient’s mood felt lifted, and her sleep pattern improved from an excess of 14 hours of sleep a day to 8 hours a day. The patient also reported an increase in energy and was able to resume her daily activities (5).
Further investigations about the precise underlying mechanisms are still required. Scientists also stress that while the focus of research has been on the alkaloids (namely mesembrine and mesembrenone), the non-alkaloid components may provide an entirely new field for sceletium research. There are also several other species of sceletium that may prove to have medicinal benefits.
In studies of healthy adult participants taking 8mg or 25mg of kanna extract daily for three months, there were no negative changes in blood pressure, pulse or breathing rate; there were also no subjectively reported side-effects (6).
According to a toxicological safety assessment of sceletium tortuosum extract in rats, no treatment-related adverse effects were observed in rats during the 14- or 90-day studies, even when given higher than recommended dosages (600mg/kg) 7.
There have been some reports of headaches, loss of appetite and intoxication in people who use too much or who chew kanna shortly after fermentation (8).
Due to its effect on serotonin levels, it is possible that supplementation can interfere with selective serotonin reuptake inhibitors prescribed for depression.
More studies are needed to determine if there are any side effects with long-term use.
While there is no standard dosage, studies of kanna have used the brand name Zembrin at doses of 8-25mg prior to cognitive testing. This product contains a 2:1 concentration of sceletium tortuosum.
More in-depth studies and trials are needed to determine the safest and most efficacious dosages.
Kanna (sceletium tortuosum) has been used in traditional South African medicine for centuries to help boost mood and to reduce stress, anxiety and depression. While it has a long history of traditional use, it has not been as well-researched in humans compared to other medicinal herbs.
Mesembrine and mesembrenone are the two main alkaloids identified, and are what researchers believe give this herb its mood-enhancing and anti-depressant properties.
While short-term use appears to be safe, further placebo-controlled clinical studies on kanna and its purported uses are needed before establishing its efficacy and safety with long-term use.
Researchers remain hopeful that this herb holds the potential to help people living with anxiety, depression and chronic stress.