Chen 2015.

Study characteristics
Methods	Study design: randomised controlled trial Study grouping: parallel group
Participants	Baseline characteristics Aromatherapy Age (mean ± SD): 33.1 ± 6.8 Sex (N (% female)): 53 (100%) Sample size: 53 Years of experience (mean ± SD): 8.0 ± 6.0 Control (no intervention) Age (mean ± SD): 33.3 ± 6.5 Sex (N (% female)): 57 (100%) Sample size: 57 Years of experience (mean ± SD): 8.4 ± 6.1 Overall Age (mean ± SD): 33.2 (NR) Sex (N (% female)): 110 (100%) Sample size: 110 Years of experience (mean ± SD): 8.2 (NR) Included criteria: female nursing staff, participants were chosen by applying the following criteria: displaying more symptoms of stress than the average of 4.6, scheduled to work over seven consecutive days, ages and working years. The criteria possessed by the experimental group included: able to communicate with researchers, willing to participate in the project, not allergic to lavender, not suffering from any form of liver or kidney dysfunction, and with normal olfactory functions. Excluded criteria: NR Pretreatment: comparisons of control variables (ages, work experiences, working years, levels of education and promotion potentials) between the experimental and the control group showed no significant statistical distribution variance. Differences in the number of the stress symptoms on the pre‐test day between the experimental group and the control group did not have a statistical significance. Compliance rate: NR Response rate: not able to assess. Purposive sampling. Type of healthcare worker: exclusively female nurses.
Interventions	Intervention characteristics Aromatherapy Type of the intervention: Intervention type 2 ‐ to focus one’s attention away from the experience of stress Description of the intervention: nurses in the experimental group wore bottles of 3% lavender oil hung in front of their right chests. On the first day of the study, the nurses in the experimental group began to wear the lavender oil bottle at the start of their shifts, and wore the necklaces at all times while working for their next four working days. Additionally, the nurses were required to rate their job stress‐related symptoms before the end of their shift every day for one pre‐test day and four posttest days. The number of sessions: NA Duration of each session on average: NA Duration of the entire intervention: 4 days Duration of the entire intervention short vs long: Short Intervention deliverer: NA Intervention form: Individual Control (no intervention) Type of the intervention: Placebo Description of the intervention: But the nurses in the control group wore bottles without lavender oil. Concurrently, the nurses in the control group were still required to write down their job stress‐related symptoms before the end of their shifts on the pretest day and each of the four posttest days. The number of sessions: NA Duration of each session on average: NA Duration of the entire intervention: NA Duration of the entire intervention short vs long: NA Intervention deliverer: NA Intervention form: NA
Outcomes	Number of Job stress‐related symptoms Outcome type: ContinuousOutcome
Identification	Sponsorship source: NR Country: Taiwan Setting: Teaching hospital Comments: NR Authors name: Li Fang Institution: Department of Nursing, Meiho University, Email: fangli72@yahoo.edu.tw Address: 23 Pingguang Road, Neipu Shiang, Pingtung County 912, Taiwan. Time period: NR
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Subsequently, the 110 nurses were randomly separated into two groups, one experimental group of 53 and one control group of 57."
Allocation concealment (selection bias)	Unclear risk	Difficult to judge whether participants and/or investigators could possibly foresee assignment, but the outcomes are not likely to be influenced.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "Participants of the control group pinned small empty bottles on their clothes on the right chest. Some participants of the control group might note that the small bottle would not decrease stress because it had no odour. When participants in the experimental group received small bottles containing lavender oil and experienced the smells, they might know there was something in the bottle that might make differences." Placebo control group.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Participants were blinded and outcomes are PROs.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not mentioned explicitly, but it appears that there is no loss to follow‐up.
Selective reporting (reporting bias)	Unclear risk	No trial registration or study protocol reported, nor did we find one online No indication of selective reporting.
Other bias	Unclear risk	Compliance rate not reported. Response rate not able to assess.‘Loosely’ validated outcome measure.