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Sceletium tortuosum

Also known as Kanna, sceletium tortusoum is a herb that is traditionally chewed prior to stressing endeavours. It suggest that it may play a role in reducing state anxiety although more evidence is required.

Our evidence-based analysis on sceletium tortuosum features 24 unique references to scientific papers.

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Summary of Sceletium tortuosum

Primary information, health benefits, side effects, usage, and other important details

Sceletium tortuosum is a herb known as Kanna which is traditionally known as a psychoactive herb. It is not known to be hallucinogenic nor habit forming but is taken prior to stressing events such as hunting (traditional use) for its cognitive effects.

Limited evidence does not suggest any improvement in reaction time or many parameters of cognitive performance such as memory although there may be an attenuation of state anxiety. State anxiety refers to the increase in anxiety experienced during a high stress event (such as a cognitive or physical test) and administration of Kanna prior to these events may reduce how much anxiety is experienced and thus the deleterious effects of anxiety on performance.

While the mechanisms as to why Kanna exerts these effects is not conclusively known, it is known to influence the amygdala of the brain (a brain region central in emotional processing) and is known to also have inhibitory effects on both the serotonin transporter as well as an enzyme known as phosphodiesterase 4 (PDE4); both of these proteins existing in the amygdala.

While there is not enough evidence to currently recommend Kanna, its main role of reducing state anxiety appears promising and there are a few other claims (such as antidepressive effects) which remain untested.

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How to Take

Recommended dosage, active amounts, other details

Currently studies using Kanna have used the brand name Zembrin® at doses of 8-25mg prior to cognitive testing. This brand name is a 2:1 concentration of Kanna based on dry weight and is considered equivalent to 16-50mg of the dry weight of the plant itself.

Kanna has been studied as oral administration (capsules) but traditionally the leaves have been chewed and saliva swallowed for similar effects.

Optimal frequency of dosing (ie. either only on testing days or daily) is currently not known.

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Human Effect Matrix

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The Human Effect Matrix summarizes human studies to tell you what effects Sceletium tortuosum has on your body, how much evidence there is, and how strong these effects are.

Full details are available to Examine members.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
grade-c Minor - See study
In high cognitive load tests, there appears to be a reduction in state anxiety (anxiety that arises during the testing) associated with Kanna compared to placebo. This reduction in anxiety does not occur during low load tests, and chronic anxiety has not yet been assessed.
grade-c Minor - See study
A general increase in cognition has been noted with Kanna usage prior to testing in otherwise healthy middle-aged adults, potentially related to the reduction in state anxiety during testing.
grade-c Minor - See study
According to the CNS Vital SignR test in middle aged adults, pre-testing administration of Kanna appeared to increase executive function when compared to placebo.
grade-c Minor - See study
There appeared to be a barely significant increase in self-reported sleep quality with Kanna usage compared to placebo when taken prior to a cognitive test.
grade-c - - See study
Three weeks Kanna usage does not appear to influence blood pressure compared to placebo.
grade-c - - See study
Three weeks Kanna usage does not appear to influence heart rate when compared to placebo.
grade-c - - See study
Acute supplementation of Kanna prior to testing does not appear to influence acute memory formation or retention when compared to placebo.
grade-c - Very High See 2 studies
In response to cognitive testing involving reaction time, administration of Kanna prior to testing does not appear to outperform place in improving reaction time.
grade-c - - See study
While there are isolated instances of increased well-being, they do not appear to occur frequently enough in otherwise healthy adults to cause a whole-group increase in well-being.

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Things to Note

Is a Form Of

Primary Function:

Also Known As

Kanna, Channa, Kougoed

Caution Notice

May interfere with neurally active pharmaceuticals due to having a similar mechanism

  • Kanna is referred to as a hallucinogen, but does not appear to have this property when taken in isolation

  • Due to having high affinity for the serotonin transporter, it is plausible that Kanna can interfere with SSRI pharmaceuticals

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Click here to see all 24 references.