Kanna is a common name for Sceletium tortuosum. It is often discussed for possible effects on stress, mood and attention. The research is interesting, but it is not a blanket finding that any kanna tablet will produce those benefits.
Stress-related findings
Small studies of particular standardized extracts have examined short-term responses to stressful tasks. Some reported signals of an effect. Different extracts, doses and study methods make it hard to apply one result to every formula on a shelf.
Mood and attention
Investigators have also studied mood-related measures and cognitive flexibility. The available human work is limited in size and duration. It does not prove that kanna treats a mood disorder or consistently improves daily concentration. Consumer accounts are not a replacement for controlled research.
Read the product, not just the plant name
Look for the amount of extract per serving, any alkaloid specification and the full ingredient list. A combination tablet cannot be assumed to behave like the single extract used in a study. Review cautions and possible interactions with medicines affecting the nervous system. Batch-linked testing helps clarify what was measured in a finished product.
The defensible conclusion is that kanna deserves further study. Claims for a particular product should be judged against its actual formulation and the narrow scope of the human evidence.
Sources: human tolerability study, cognitive study and research review.
