Key Terms
Concise definitions for terms used throughout this guide
The following definitions are provided for quick reference. Full context for each appears in the relevant section of the guide.
Adenosine
A molecule that accumulates in the brain across the day and produces the felt sense of sleepiness by binding to adenosine receptors. Caffeine works by blocking these receptors rather than clearing adenosine itself.
Aromatase
An enzyme that converts testosterone into oestrogen. Alcohol increases aromatase activity, contributing to its testosterone-suppressing, oestrogen-raising effect.
Cross-Sectional Study
A study that measures exposure and outcome at a single point in time, which can identify an association but cannot establish which came first — distinct from a longitudinal study, which tracks the same subjects over time and can better support causal claims.
Downregulation
A reduction in the brain's baseline receptor sensitivity in response to repeated, elevated stimulation — the mechanism behind tolerance, where progressively larger doses are needed to achieve the same effect.
Reverse Causation
When the assumed cause and effect are actually reversed — for example, a pre-existing condition driving increased use of a substance, rather than the substance causing the condition.