A Preliminary Investigation of Individual Differences in Subjective Responses to D-Amphetamine, Alcohol, and Delta-9-Tetrahydrocannabinol Using a Within-Subjects Randomized Trial

• Published in: PloS one Vol. 10; no. 10; p. e0140501
• Main Authors: Wardle, Margaret C., Marcus, Benjamin A., de Wit, Harriet
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 29.10.2015; Public Library of Science (PLoS)
• Subjects: Adult; Alcohol; Alcohol use; Alcohols; Amphetamine; Amphetamines; Correlation; Dextroamphetamine - administration & dosage; Dextroamphetamine - pharmacology; Dronabinol - administration & dosage; Dronabinol - pharmacology; Drug abuse; Drug Tolerance; Drug use; Drug Users; Drugs; Ethanol - administration & dosage; Ethanol - pharmacology; Female; Healthy Volunteers; Humans; Impulsive behavior; Laboratories; Male; Marijuana; Neurosciences; Personality; Personality Inventory; Personality traits; Psychiatry; Psychopharmacology; Stimulants; Studies; Substance-Related Disorders - epidemiology; Substance-Related Disorders - metabolism; Surveys and Questionnaires; Tetrahydrocannabinol; Well being; Within-subjects design; Young Adult; United States > US; Chicago Illinois
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0140501

Polydrug use is common, and might occur because certain individuals experience positive effects from several different drugs during early stages of use. This study examined individual differences in subjective responses to single oral doses of d-amphetamine, alcohol, and delta-9-tetrahydrocannabinol (THC) in healthy social drinkers. Each of these drugs produces feelings of well-being in at least some individuals, and we hypothesized that subjective responses to these drugs would be positively correlated. We also examined participants' drug responses in relation to personality traits associated with drug use. In this initial, exploratory study, 24 healthy, light drug users (12 male, 12 female), aged 21-31 years, participated in a fully within-subject, randomized, counterbalanced design with six 5.5-hour sessions in which they received d-amphetamine (20mg), alcohol (0.8 g/kg), or THC (7.5 mg), each paired with a placebo session. Participants rated the drugs' effects on both global measures (e.g. feeling a drug effect at all) and drug-specific measures. In general, participants' responses to the three drugs were unrelated. Unexpectedly, "wanting more" alcohol was inversely correlated with "wanting more" THC. Additionally, in women, but not in men, "disliking" alcohol was negatively correlated with "disliking" THC. Positive alcohol and amphetamine responses were related, but only in individuals who experienced a stimulant effect of alcohol. Finally, high trait constraint (or lack of impulsivity) was associated with lower reports of liking alcohol. No personality traits predicted responses across multiple drug types. Generally, these findings do not support the idea that certain individuals experience greater positive effects across multiple drug classes, but instead provide some evidence for a "drug of choice" model, in which individuals respond positively to certain classes of drugs that share similar subjective effects, and dislike other types of drugs.