Wednesday, 10 November 2010

There are always confounds

Via Barking up the Wrong Tree we find that some of the reported negative effects of alcohol and tobacco on student academic performance may be due instead to caffeine.
Using academic achievement as the key outcome variable, 7377 Icelandic adolescents were surveyed for cigarette smoking, alcohol use, daytime sleepiness, caffeine use, and potential confounders. Structural equation modeling (SEM) was used to examine direct and indirect effects of measured and latent variables in two models: the first with caffeine excluded and the second with caffeine included. A substantial proportion of variance in academic achievement, which might otherwise have been attributed to the harmful effects of cigarette smoking and alcohol use, was found to be attributable to caffeine. Evidence was obtained that daytime sleepiness, which was found to be independently associated with usage of licit substances (nicotine and alcohol) and caffeine, may be an important mediator of the negative impact of those substances on academic achievement. Findings suggest the importance of including measurements of caffeine consumption in future studies of adolescent substance use.
The article is available via PubMed for folks with ScienceDirect subscriptions.

Odds that this kind of work leads to calls for regulation of energy drinks rather than easing back on regulation of alcohol and tobacco?


  1. Bah! Everyone knows real students take no-doze anyway...

  2. Hmm. I'm under the impression that part of the reason for this result is because licit substance use causes an increase in caffeine use - so the total impact of licit substances will be the sum of the direct effect and some component of the caffeine effect.

    The belief in this causal mechanism comes from years of intensive study of the interaction between alcohol, work/study, and caffeine consumption choices made by myself.