The Effects of Lemon Essential Oil Inhalation on Attention in Children With Attention Deficit Hyperactivity Disorder (ADHD)

Lemon Essential Oil Inhalation Improves Sustained Attention in Children With Attention-Deficit/Hyperactivity Disorder: A Placebo-Controlled Trial

This randomized, placebo-controlled clinical trial aims to evaluate the acute effects of lemon essential oil inhalation on sustained attention and visual memory in children diagnosed with Attention-Deficit/Hyperactivity Disorder (ADHD). Fifty-two medication-naive children aged 9-16 were randomized to receive either lemon oil or placebo inhalation before cognitive assessments. Primary outcome was sustained attention performance. The study found significant improvements in attention scores in the lemon oil group.

Study Overview

• Status: Completed
• Conditions: Attention Deficit Disorder With Hyperactivity (ADHD); Aromatherapy; Essential Oil; Non-Pharmacological Interventions; Sustained Attention
• Intervention / Treatment: Other: Lemon Essential Oil Inhalation; Other: placebo inhalation

Detailed Description

This randomized, placebo-controlled, single-blind clinical trial investigates the acute effects of lemon essential oil (LEO) inhalation on sustained attention and visual memory in children with attention-deficit/hyperactivity disorder (ADHD). Essential oils, particularly those rich in monoterpenes such as limonene, have demonstrated neuroactive properties through cholinergic modulation and limbic-prefrontal engagement via the olfactory pathway.

Fifty-two children aged 9-16 years, newly diagnosed with ADHD and not receiving any pharmacological treatment, were randomized to either the LEO group or the placebo group. Participants in the LEO group inhaled 5 drops of 100% pure Citrus limon essential oil via a cotton pad for five minutes prior to cognitive testing. The placebo group received an identical application with odorless distilled water.

Cognitive performance was assessed at baseline and 30 days later using the D2 Attention Test (primary outcome) and the Benton Visual Memory Test (secondary outcome). The entire intervention was conducted under standardized conditions, with blinded outcome assessment and strict adherence to procedural fidelity.

This study is the first to evaluate the short-term cognitive effects of lemon essential oil inhalation in children with clinical ADHD and aims to provide evidence for potential non-pharmacological support strategies.

• Study Type: Interventional
• Enrollment (Actual): 52
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Istanbul, Turkey (Türkiye)
    • Basaksehir Cam ve Sakura City Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Children aged 9 to 16 years
• Diagnosis of Attention Deficit Hyperactivity Disorder (ADHD) based on DSM-5 criteria
• Medication-naive (not currently using or previously treated with pharmacological agents for ADHD)
• No chronic medical or psychiatric comorbidities
• Capable of completing standardized cognitive assessments (e.g., D2 Attention Test, Benton Visual Memory Test)
• Written informed consent obtained from a parent or legal guardian
• Written assent obtained from the child

Exclusion Criteria:

• Lack of written parental consent or child assent
• Inability to comply with the study protocol (e.g., refusal to complete cognitive testing or intervention procedure)
• Current or prior use of ADHD medication
• Presence of moderate-to-severe ADHD symptoms requiring immediate pharmacological treatment (based on AACAP 2020 and NICE 2019 guidelines)
• Presence of any chronic medical or psychiatric comorbid condition
• Diagnosis not confirmed by a board-certified child and adolescent psychiatrist

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Supportive Care
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Lemon Essential Oil Inhalation (LEO); Participants in this arm received a single-session inhalation of 100% pure lemon essential oil (Citrus limon) via a sterile cotton pad. Five drops of essential oil were applied to the pad, which was held approximately 5 cm from the participant's nose. The child inhaled the scent for 5 minutes under supervision in a clinical setting. Neuropsychological testing (D2 Attention Test and Benton Visual Memory Test) followed immediately after inhalation.	Other: Lemon Essential Oil Inhalation; This intervention consists of a single-session, short-term olfactory exposure to 100% pure lemon essential oil (Citrus limon, ISO 9235 compliant, GC-MS confirmed composition: limonene 67.2%, β-pinene 12.3%, γ-terpinene 9.8%). Five drops were applied to a sterile cotton pad and held approximately 5 cm from the participant's nose. Participants inhaled the aroma for 5 minutes under direct supervision in a quiet, odor-free clinical setting. This intervention was administered immediately prior to standardized neuropsychological assessments measuring attention and visual memory. No ingestion or topical application occurred.; Other Names: Citrus limon aroma; LEO
Placebo Comparator: Placebo Inhalation (Distilled Water); Participants in this arm received a single-session inhalation of distilled water as placebo. Five drops of distilled water were applied to a sterile cotton pad, which was held approximately 5 cm from the participant's nose. The child inhaled the scentless solution for 5 minutes under supervision. Neuropsychological testing (D2 Attention Test and Benton Visual Memory Test) followed immediately after inhalation.	Other: placebo inhalation; The placebo condition involved the same protocol as the intervention group, using five drops of distilled water applied to a sterile cotton pad. The pad was held approximately 5 cm from the participant's nose, and inhalation lasted for 5 minutes. The procedure was designed to mimic the intervention without olfactory stimulation, ensuring consistency in timing, setting, and administration method.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in D2 Attention Test Total Performance Score (TN-E)	The D2 Attention Test evaluates sustained attention and concentration performance. The TN-E (Total Number of Correct Items minus Errors) score reflects attentional capacity. A higher post-intervention TN-E score indicates improved attention. The difference between baseline and Day 30 scores will be compared between the lemon essential oil group and placebo group.	Baseline and Day 30 (after intervention)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in Benton Visual Retention Test (BVRT) Score	The Benton Visual Retention Test assesses visual memory and visuospatial construction skills. Scores range based on correct reproductions of geometric figures. The change in BVRT scores from baseline to Day 30 will be analyzed to assess the impact of lemon essential oil inhalation versus placebo.	Baseline and Day 30 (after intervention)

Collaborators and Investigators

• Sponsor: Başakşehir Çam & Sakura City Hospital

Study record dates

Study Major Dates

• Study Start (Actual): February 15, 2022
• Primary Completion (Actual): September 30, 2023
• Study Completion (Actual): September 30, 2023

Study Registration Dates

• First Submitted: December 24, 2025
• First Submitted That Met QC Criteria: May 8, 2026
• First Posted (Actual): May 14, 2026

Study Record Updates

• Last Update Posted (Actual): May 14, 2026
• Last Update Submitted That Met QC Criteria: May 8, 2026
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: Aromatherapy; Non-Pharmacological Interventions; Essential Oils; Pediatric Neuropsychology; Attention Deficit Disorder with Hyperactivitiy (ADHD)
• Additional Relevant MeSH Terms: Mental Disorders; Neurodevelopmental Disorders; Attention Deficit and Disruptive Behavior Disorders; Attention Deficit Disorder with Hyperactivity
• Other Study ID Numbers: 10.06.2021-21

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Individual participant data (IPD) will not be shared for this study due to ethical considerations, privacy protection regulations involving minors, and the absence of prior consent for data sharing beyond the scope of this trial. Additionally, the study was conducted with a small sample size from a single center, limiting the generalizability and reuse of anonymized data for broader analysis.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No