Knowledge
Understanding intensity.
These texts put research on intoxicating plant products into context. Strength means the measured concentration of the main active compound. It is neither an efficiency rating nor a measure of the quality of an experience.
From the 1970s to today.
In the 1970s, some tested samples had concentrations in the low single digits. Today, varieties are advertised with figures of up to 41 percent.
Sources: PubMed · Historical review · 1988 · Anesia Seeds · Think Tank · 2026
The changing plant.
Measured strength has increased substantially over the decades. A US analysis published in 2013 estimated a six- to sevenfold rise in average active-compound concentration between the 1970s and the 2000s after accounting for sample quality.
In Europe, a study documented roughly a doubling of the average concentration in sampled herbal material between 2006 and 2016. The 2026 European report describes a wider range of particularly strong products.
These data describe different markets and periods. A higher concentration does not automatically mean a proportionately more intense personal experience.
Sources: Sevigny · Drug Testing and Analysis · 2013 · Freeman et al. · Addiction · 2019 · EUDA · European Drug Report · 2026
Strength and mental health.
Daily use of particularly strong products is associated with a higher risk of severe mental disorders involving impaired contact with reality. A 2019 international case-control study found this association compared with people who had never used them.
The study examines the relationship between product strength, daily use and specific disorders. As an observational study, it does not establish strength alone as the cause.
More effect. Not more clarity.
In a controlled 2018 study of 17 adults who used infrequently, the higher dose produced more pronounced acute impairment of thinking and motor performance, alongside more adverse effects. The method of administration also influenced intensity.
The study examined short-term effects on performance. Its findings distinguish measured strength, the amount taken and the effects on thinking and motor performance.
Strength and dependence.
A 2020 study of 1,087 young adults found more problematic use among those reporting stronger products. Strength was reported by participants.
A 2023 study distinguished preferred strength from measured concentration: preference for particularly strong products was associated with dependence, whereas measured concentration was not. This finding was not adjusted for frequency of use.
Sources: Hines et al. · JAMA Psychiatry · 2020 · Petrilli et al. · Addictive Behaviors · 2023
Editorial date: September 2026