Case Review Finds Insufficient Evidence That Kratom Alone Causes Severe Adverse Effects

Why it matters

A comprehensive systematic review of 95 kratom-related case reports finds that 91% of fatal cases involved multiple substances, while nearly half of surviving cases did not. The analysis reveals widespread incomplete toxicology testing that may overestimate kratom's role in adverse outcomes.

The big picture

Researchers from TRC Companies analyzed all published case reports of acute kratom adverse effects through June 2024. Among 55 toxicologically confirmed cases, they found clear patterns of polypharmacy confounding causation attribution. Notably, several deaths initially attributed solely to kratom were later found to involve additional drugs upon reexamination, highlighting how incomplete testing creates false attribution.

Key findings

• 95% of reviewed cases involved kratom exposure claims; only 55 (58%) had toxicological confirmation of mitragynine
• 91% of fatal cases involved confounding substances (benzodiazepines, opioids, SSRIs, antipsychotics) versus 35% of surviving cases
• When mitragynine alone was detected in surviving cases, seizures were the most common adverse effect (6 of 11 cases)
• Estimated death rate from kratom-only use approximately 1,390 times lower than any opioid use and 15,926 times lower than heroin
• Polypharmacy was statistically significantly associated with death (p=0.0002)

What they say

Authors conclude: 'Currently, the literature provides insufficient evidence to support the claim that kratom consumption alone increases the risk of severe acute adverse health effects. More research is necessary to isolate the effects of kratom from those of polypharmacy.'

Bottom line

Most kratom-attributed deaths actually involved multiple drugs; without complete toxicology testing, adverse effects attributed to kratom are likely significantly overstated.