July 6, 2022

Bitter Orange: Another Tool to Improve Sleep

Findings from a randomized, controlled study
Postmenopausal women with sleep disturbances found better slumber through aromatherapy with Citrus aurantium oil 5 minutes, twice daily, 4 days a week.


Abbaspoor Z, Siahposh A, Javadifar N, Faal Siahkal S, Mohaghegh Z, Sharifipour F. The effect of Citrus aurantium aroma on the sleep quality in postmenopausal women: a randomized controlled trial. Int J Community Based Nurs Midwifery. 2022;10(2):86-95.

Study Objective

To determine whether inhalation of Citrus aurantium (bitter orange) daily over 4 weeks would improve the sleep of postmenopausal women

Key Takeaway

Inhalation of Citrus aurantium for 5 minutes, twice daily, 4 days a week for 4 weeks resulted in a significant improvement in sleep for postmenopausal women. Sleep complaints affect a significant portion of this subpopulation.


Randomized, controlled study in which both the participants and the researchers were blinded to the treatment condition


Eighty postmenopausal women, aged 45 to 60 years, participated in this study. Inclusion criteria were the ability to read and write, cessation of menses for 12 months or more, 5 or more on the Pittsburgh Sleep Quality Index questionnaire, no medical or mental disorder, available medical records, no alcohol, and no stressful events in the 6 months prior.


Participants placed 2 drops of oil on their forearm and inhaled the aroma from a distance of 30 cm away with normal breathing for 5 minutes twice daily (10 am and 10 pm). The treatment group received 10% Citrus aurantium oil (mixed in odorless almond oil diluted with propylene glycol), while the control group received odorless almond oil, which was also diluted with propylene glycol. They inhaled the aroma 4 consecutive days each week for 4 weeks.

Study Parameters Assessed

The Pittsburgh Sleep Quality Index was the single outcome measure. The PSQI is a well-validated and commonly used measure of subjective sleep, which is used worldwide.

Primary Outcome

This study determined whether sleep improved subjectively with bitter orange inhalation treatment.

Key Findings

The postmenopausal women who used the Citrus aurantium oil had a statistically significant improvement in their subjective sleep, with the PSQI dropping from 12.08 to 5.75 (P<0.001). The PSQI was unchanged in the control group.


The research center at Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran funded this study.

Practice Implications & Limitations

People worldwide have sleep complaints, and the number has been growing over the last several years.2 Sleep problems contribute to a wide variety of other medical disorders, from anxiety and depression to cardiovascular disease, inflammatory conditions, and obesity, to name just a few.3 With such high prevalence and consequences, finding effective sleep treatments that are easily implemented is a high priority for researchers and clinicians.

Inhalation aromatherapy for sleep has a historical precedent, and research in this area is accumulating.4 Reviews have found evidence for use of bergamot, cedar, lemon, rose, sweet orange, valerian, and other essential oils.5 When the essential oil is smelled, molecules stimulate the olfactory system, which in turn signals the limbic system and autonomic nervous system. Essential oil molecules in the respiratory tract can directly stimulate the central nervous system.6

A meta-analysis in 20217 found that aromatherapy has variable effects on different sleep disorders. Lavender is the most commonly used aromatherapy for sleep, particularly with insomnia. The effects were greater when just a single oil was used, rather than a mixture of multiple essential oils. Results were also greater in those with insomnia compared to those with a general sleep complaint.

The bitter orange essential oil used in this study, made from the flowers, is also called neroli oil. The main constituent (35%) is linalool, which has several properties, including anxiolytic, antioxidant, antimicrobial, cytotoxic, and antidiabetic.8 Linalool is present in lavender essential oil also.

Benefits of inhalation aromatherapy for sleep are that it is easily self-administered, does not take much time, and is relatively inexpensive. Challenges can be incorporating this treatment into the daily lifestyle; the 10 am dose may be particularly difficult to incorporate for people who are working.

Reviews have found evidence for use of bergamot, cedar, lemon, rose, sweet orange, valerian, and other essential oils.”

Sleep disorders among women increase with advancing age. The estimated prevalence of moderate to severe sleep disordered breathing is 4% to 50% in women, with postmenopausal women having 3 to 6 times the prevalence of younger women. Nonrestorative sleep is reported by 26% to 42% of women.9 Yet far fewer women are diagnosed with a sleep disorder. In a 2012 study, 34% of participants (the majority women) who were previously diagnosed with primary insomnia were found to have another sleep disorder such as sleep apnea syndrome or periodic limb movement disorder.10

In this study the primary outcome measure was the Pittsburgh Sleep Quality Index, or PSQI. The PSQI is a well-validated questionnaire in many populations.11 The 24 questions are evaluated in terms of 7 subscales. The cut-off for sleep disturbance is 5 or more.

Although the PSQI is a well-validated subjective measure of sleep, it does not diagnose specific sleep disorders. There are over 60 sleep disorders.12 Unfortunately, the vast majority of sleep disorders are undiagnosed, leading to increased personal health risks and societal costs. One concern of simply relying on subjective sleep improvement is that an underlying sleep disorder may go undiagnosed and untreated. Although this treatment with bitter orange aromatherapy did bring the PSQI down significantly after the 4 weeks of treatment, the score was still above the cut-off for disrupted sleep, at 5.75±1.33 (P<0.001). This indicates the participants still have clinically significant sleep disruption.

Therefore, in a clinical setting, it would be appropriate to do further screening and assessment for all 60 sleep disorders, followed by treatment. Given the high number of people with subjective sleep complaints and the ease of inhalation aromatherapy, this is a welcome addition to the clinical tool kit. The bitter orange aromatherapy could be used for subjective relief while other sleep disorders are being ruled out.

Categorized Under


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