| Effect | Increase |
| Trial Design | Double blind |
| Trial Length | n/a |
| Number of Subjects | 400 |
| Sex | n/a |
Anxiety, as assessed by self-report surveys, was significantly higher than placebo in persons with a single-nucleotide polymorphism (TT) of the adenosine A2A receptor after consuming two small (100,150mg) doses of caffeine.
Evidence for a genetic connection between anxiety and caffeine.
Also increased anxiety in persons unaccustomed to caffeine intake on a daily basis independent of genotype.
