Bidirectional interactions between acute psychosocial stress and acute intravenous alcohol in healthy men

Abstract

Background: The biological mechanisms by which acute stress increases alcohol consumption are unclear. One potential mechanism is that stress acts by altering the pharmacological and subjective effects of alcohol. Acute stress produces a cascade of physiological and psychological effects, each with a distinctive time course. In this study, we investigated whether different phases of response to an acute stress alter the subjective effects of intravenous alcohol, by administering the drug at 2 different times after the stress.

Methods: Healthy men (n = 25) participated in 2 sessions: 1 with the Trier Social Stress Test and the other with a nonstressful control task, each followed by infusions of intravenous alcohol (targeting 40 mg% in 5 minutes) and placebo. One group of participants received alcohol within 1 minute of completing the tasks (Alc0, n = 11), followed by placebo 30 minutes later. In the other group (Alc30, n = 14), the order of alcohol and placebo infusions was reversed. Subjective effects (i.e., anxiety, stimulation, want more) and physiological measures (heart rate, blood pressure, salivary cortisol) were measured before and at repeated intervals after the tasks and infusions.

Results: Stress did not change the subjective effects of alcohol in either group. However, when individual differences in alcohol responses were considered, stress differentially altered the stimulant-like and sedative effects of alcohol. Among individuals who exhibited predominantly stimulant responses to alcohol in the nonstressful condition, stress decreased the stimulant-like effects of alcohol and "wanting more." By contrast, among participants who did not report stimulation after alcohol in the control session, stress decreased the sedative effects and increased "want more." In addition, alcohol administered immediately after the Trier Social Stress Test dampened cortisol responses yet prolonged negative subjective responses to the stress.

Conclusions: These findings demonstrate that there are bidirectional relationships between alcohol and stress. Alcohol influences responses to stress, and stress changes reactions to alcohol, depending on an individual's pattern of response to alcohol. This study highlights the fact that stress-alcohol interactions vary among individual drinkers, suggesting that the effects of stress on motivation to drink alcohol may also differ between individuals.

Figure 1

Schematic showing the timing of tasks, infusions and collection of cardiovascular, hormonal and subjective measures during the experimental sessions.

Figure 2

Subjective responses to intravenous alcohol and placebo after the control task. The graphs show responses to infusion 1 during the control session among participants in group Alc0 (N=11, alcohol, filled bars) and group Alc30 (N=14, placebo, open bars). Data indicate mean±SEM change from pre-infusion baseline for the DEQ (left hand side) and BAES (right hand side). Asterisks indicate a significant difference between the groups (Student's independent samples t-test, *p<0.05 **p<0.01).

Figure 3

Individual differences in response to alcohol after the TSST and non-stressful tasks. Top left graph shows scores of BAES Stimulation for all participants after the non-stressful task and classification of subsets of participants. Bar charts illustrate changes (from pre-infusion baseline, mean±SEM) in subjective responses to alcohol after the TSST (shaded bars) and control task (open bars) for participants classified as Stimulant or Non-Stimulant Responders. Asterisks indicate a significant difference between the groups (Student's independent samples t-test, p<0.05) and # indicates a significant difference between the tasks (Student's Paired t-test, p<0.05).

Figure 4

Effects of intravenous alcohol upon responses to acute stress. Data indicate mean±SEM subjective and cortisol responses to stress as a function of time among participants in group Alc0 (open symbols) and Alc30 (closed symbols). The shaded bar indicates when tasks were performed and arrows indicate when infusions were delivered.