Background and purpose: We previously found that for both men and women odors influence mood, which in turn influences pain unpleasantness perception. Others showed that the steroid androstadienone modulates mood differently in men and women, improving mood in women and worsening it or leaving it unchanged in men. Based on its dissociable effect on mood, we hypothesized that women exposed to androstadienone would report lower pain unpleasantness than when exposed to the vehicle, while men would show no change or the reverse pattern. Because of the expected beneficial effect of pleasant odors on mood in both men and women, all subjects should report lower pain unpleasantness when exposed to the pleasant odor compared to the unscented air.
Methods: In one session subjects were exposed to: (1) androstadienone diluted in a vehicle while breathing unscented air and (2) androstadienone in vehicle while breathing a pleasant odorant. In another session they were exposed to: (1) vehicle and unscented air and (2) vehicle and a pleasant odorant. Phasic contact heat was used to induce pain.
Results and conclusions: Planned comparisons confirmed that, in the absence of pain, androstadienone improved mood only in women, while the pleasant odorants improved mood for all subjects. However, these positive mood changes did not persist with the introduction of pain. Consistent with the absence of positive mood changes, pain unpleasantness was not modulated. Unexpectedly, the presence of androstadienone increased perceived pain intensity especially in women, suggesting an effect of androstadienone on pain perception, independent of mood changes. Heightened attentional state may be responsible.