A study found that subjective amphetamine response changed the statistical relationship between negative emotionality and reported alcohol use. The result was not evidence that an amphetamine challenge can reliably forecast an individual’s future drinking.
Allen and Gabbay assessed personality and alcohol or drug-use history in healthy young adults. Participants then received a 10-mg d-amphetamine challenge, with stimulation measured using a rating scale.
The researchers used regression analyses to examine negative emotionality, stimulant response and their interaction. Negative emotionality was a personality measure, not a diagnosis, and the stimulation rating was not an amphetamine concentration.
Negative emotionality was associated with heavier alcohol-use measures when it co-occurred with a stronger stimulant response. Those measures included alcohol consumption, binge-drinking episodes and intoxication frequency.
Negative emotionality alone was not significantly related to the measured use outcomes. The challenge response independently related to whether participants had used an illicit drug, while the corresponding alcohol-history finding was only a trend.
A statistical interaction means the association involving one variable depended on the level of another in the fitted model. It does not establish that personality caused drinking through a particular drug response or that either measure will predict new cases accurately.
Substance-use information was retrospective. The study did not follow initially substance-naive people to determine who later developed problems.
The challenge lacked a placebo condition, leaving expectancy as a possible influence on subjective ratings. Only one amphetamine dose was examined, and reported substance-use history may be imprecise.
The findings support further research on interacting individual differences. They do not justify diagnosing addiction vulnerability, choosing treatment or making a forensic judgment about a particular person’s conduct from a stimulation score. Actual function, exposure and event-specific evidence remain separate questions.
Related reading: Self-report and urine outcomes can disagree.