Role of expectations and pleasantness of essential oils in their acute effects

Abstract

Effects of inhaled essential oils (EOs) cannot be explained by pharmacological mechanisms alone. The study aimed to investigate the effects of pleasantness of and expectancies evoked by EOs. A double-blind experiment with a within-subject design was carried out with the participation of 33 volunteering adults (15.2% male; mean age 37.7 ± 10.90 years). Participants were exposed to three EOs (rosemary, lavender, and eucalyptus) for three minutes in a quasi-random order, expectations were simply assessed prior to exposure. Subjective (perceived) changes in alertness, heart rate (HR), and blood pressure (BP), and objective changes in HR, BP, and indices of heart rate variability were recorded. Significant group-level differences in changes in alertness and no differences for the cardiovascular variables were found. Participants' expectations predicted changes in alertness in the case of rosemary and lavender oils but had no impact on cardiovascular variables. EOs' pleasantness had no effect on any assessed variable. Perceived changes in BP and HR were not related to the respective objective changes but were connected to perceived changes in alertness. Expectancies play an important role in the subjective effects of inhaled EOs. Perceived subjective changes are used to estimate changes in non-conscious (e.g., visceral) states.

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

“…Second, a placebo pill given with a stimulant suggestion evoked similar expectations that also predicted perceived changes. In a previous research, inhaling rosemary and lavender EOs had no impact on actual alertness; however, rosemary evoked stimulant expectations while lavender evoked sedative expectations . Moreover, perceived changes were only in accordance with participants' expectations for lavender.…”

“…Participants in the intervention groups, however, reported higher levels of perceived changes, and only perceived changes were predicted by alertness related expectations. Lavender and rosemary had no impact on actual HR and blood pressure in a previous study conducted under relaxed circumstances, but reduced both in a stress‐evoking situation (test anxiety) . It is well‐known that actual HR is barely detectable, which also means that expectations and other factors can substantially influence the perception of HR .…”

“…In addition, the boundary between expectation‐based and conditioned responses is quite vague in humans . That is to say, a considerable proportion of learned responses are represented by expectations, particularly in the case of such consciously perceived stimuli as odours …”

Mental heartbeat tracking and rating of emotional pictures are not related

“…It is well-known, however, that the association between actual (i.e., physiological) and perceived arousal is quite low, particularly if the former is not intense (Colombetti & Harrison, 2018). Perceived arousal can be substantially influenced by top-down processes, e.g., expectations (Köteles & Babulka, 2014) and false feedback on physiological changes (Piccione & Veitch, 1979;Valins, 1966). IAPS pictures (Lang et al, 2008) have a very clear message regarding the type of the emotion, which might evoke high demand characteristics.…”

Super Pill is Less Effective than an Ordinary Mint in Altering Subjective Psychological Feeling States within a Few Minutes

“…assessed using no self-report scales or assessed before and after the intervention) and subjective or perceived (i.e. assessed only after the intervention using self-report scales) effects (Babulka, Berkes, Szemerszky, & Köteles, 2017;Köteles & Babulka, 2014;Schwarz & Büchel, 2015). Expectancies usually have a greater impact on perceived effects than on the objective effects; in fact, they did not predict objective changes in many earlier studies (Babulka et al, 2017;Köteles & Babulka, 2014;Schwarz & Büchel, 2015;Szabo, Szemerszky, Dömötör, De la Vega, & Köteles, 2017;Szabo, Szemerszky, Dömötör, Gresits, & Köteles, 2017).…”