Evidence levels explained: strong, moderate, limited and anecdotal

Evidence level on SubsAtlas describes how well-studied a substance is, how consistent available research is, and what type of evidence exists. It is a quality and certainty indicator, not a safety certificate. A substance with 'strong' evidence is not necessarily safe or suitable. It means better-documented patterns exist. A substance with 'limited' evidence is not necessarily more dangerous — it may simply be less studied.

Strong evidence means multiple consistent studies exist, or official clinical or public health guidance is available for the patterns described. Alcohol and caffeine have strong evidence for their documented effects and risks. Strong evidence still does not make a substance safe, low-risk or suitable. Alcohol is a good example: strong evidence + high risk level.

• Multiple consistent research sources exist.
• Official clinical or public health guidance may be available.
• Does not mean the substance is safe, low-risk or recommended.
• Risk level is a separate assessment from evidence level.

Moderate evidence means some meaningful research exists but results are mixed, populations studied differ from broader contexts, or methodology limitations are present. Cannabis as a plant has a moderate evidence designation for most effects — some research exists but quality and consistency varies significantly across the body of literature.

Limited evidence means early, narrow or incomplete research exists. Findings should not be generalised. Uncertainty is significant. Kratom has a limited evidence designation — research is growing but remains insufficient for strong characterisation of many effects and risks.

Anecdotal evidence means patterns are reported by individuals or communities without formal study. This is the lowest confidence category. It is not research evidence. Uncertainty is high. Some fungi and botanical compounds in early research stages carry anecdotal designations.

Read evidence level alongside risk level — not instead of it. A substance can have strong evidence and high risk (alcohol). A substance can have limited evidence and unclear risk (novel compounds). Evidence level tells you about certainty; risk level tells you about concern. Both matter. Both are shown separately on every profile.