Ylang-ylang oil appears to exert a sedative-like effect, compared to a control, in some randomized controlled trials (RCTs), increasing calmness,[1][2] relaxation,[2] and skin temperature (potentially indicating a relaxed nervous system),[2] and decreasing blood pressure[2][3][4] and heart rate.[3][4] In accordance with these sedative-like effects, ylang-ylang oil decreased reaction time and how quickly participants were able to recall words in one RCT.[1] Contrastingly, ylang-ylang oil increased attentiveness and alertness in one trial[3] but not another one.[2]
However, in some RCTs[3][4][5] of ylang-ylang oil, a poor control was used: water. Water is a poor control in this context because it has no smell, meaning the participants might recognize whether they received the active intervention (ylang-ylang oil) or the control (water). This could bias the results in favor of the ylang-ylang oil. A more appropriate control would be something with a smell but no effects on the body (or at least no effects on the outcomes being studied). This might reduce the apparent effectiveness of ylang-ylang oil compared to this aromatic control and potentially give a more accurate representation of its effects.
Despite these aforementioned sedative-like effects, ylang-ylang oil did not reduce anxiety compared to a control in 3 of 4 RCTs.[5][6][7][8] Notably, in the RCT showing a reduction in anxiety, stress, and cortisol,[8] the intervention group also used lavender and bergamot oil, which also could have reduced these outcomes.[9][10] This decreases the likelihood that ylang-ylang oil was responsible for the reductions in anxiety, stress, and cortisol.
Furthermore, ylang-ylang oil has not consistently improved other outcomes alongside anxiety, such as cortisol or self-esteem, in RCTs. For example, in one RCT there were no reductions in anxiety or salivary cortisol compared to a placebo.[5] Similarly, ylang-ylang oil did not improve anxiety in a sample of nurses, though it did improve self-esteem.[7] However, in an earlier, similar trial by the same authors, ylang-ylang oil did not improve self-esteem.[11]