Effects of stress on responses to methamphetamine in humans.

RATIONALE

Studies with laboratory animals indicate that acute stress can modify both the direct effects of drugs of abuse and the tendency to self-administer drugs. Similarly, stress may also alter the acute subjective effects of drugs or the tendency to seek and consume drugs in humans.

OBJECTIVES

This laboratory-based study was designed to determine whether an acute social stressor (Trier Social Stress Test; TSST) alters subjective responses to a low oral dose of methamphetamine (METH; 10 mg) in humans.

METHODS

The study utilized a mixed within- and between-subjects design. Healthy young men ( n=28) participated in two sessions, one with stress and the other without. They were randomly assigned to two groups who received either METH ( n=16) or placebo ( n=12) on both sessions. On each session, subjects underwent the TSST or no TSST, and then ingested a beverage containing drug (10 mg METH) or placebo (PLAC). Over the next 1.5 h various self-reported mood measures and physiological measures, including salivary cortisol levels, were obtained at regular intervals.

RESULTS

Both acute stress and METH produced mood-altering and physiological effects. Stress increased ratings of anxiety immediately after the stressful task, and increased salivary cortisol levels 20 min later. METH increased feelings of stimulation, and decreased fatigue and sedation, beginning about 20 min after drug administration and peaking at 60 and 90 min. Stress dampened the early responses to METH (i.e. at 20 min), but not the later effects (60 or 90 min).

CONCLUSIONS

These results demonstrate that acute stress can dampen subjective responses to a low dose of METH, but these effects are short-lived. It remains to be determined what mechanisms mediate this effect.