No effects of rosemary and lavender essential oil and a placebo pill on sustained attention, alertness, and heart rate

Abstract

AbstractEssential oils (EOs) are widely used for various purposes, however, their claimed effects are often not supported by empirical data. Previous findings have highlighted the importance of psychological factors (e.g. expectations) in their mechanism of action. The present study investigated the effects of an ingested placebo pill and inhaled rosemary and lavender oils on alertness and heart rate, as well as actual and perceived performance in a sustained attention task. 128 young adults, randomly allocated to four groups (rosemary, lavender, placebo pill with stimulant suggestion, and control), completed a vigilance task before and after the respective intervention. Compared to the control condition, no effects of the three interventions were found on actual changes in sustained attention, alertness, or heart rate. Both EOs and the placebo pill evoked positive expectations regarding cognitive performance and alertness. Expectations predicted perceived changes in alertness and heart rate, but not in cognitive performance. No differences between the two EOs and the placebo intervention were found in any respect. Psychological mechanisms behind the effects of inhaled EOs and placebos might be overlapping.