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NCT Number: NCT07586761

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

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.

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Key information

Conditions

Attention Deficit Disorder With Hyperactivity (ADHD) Aromatherapy Attention Deficit Disorder with Hyperactivity Attention Deficit and Disruptive Behavior Disorders Essential Oil Mental Disorders Neurodevelopmental Disorders Non-Pharmacological Interventions Sustained Attention

Age range

9 year–16 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Basaksehir Cam ve Sakura City Hospital

Istanbul, Turkey (Türkiye)

About this study

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.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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

Treatment and study plan

Lemon Essential Oil Inhalation

Other

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 inhalation

Other

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.

Primary outcomes

  1. Change in D2 Attention Test Total Performance Score (TN-E)

    Time frame: Baseline and Day 30 (after intervention)

    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.

Secondary outcomes

  1. Change in Benton Visual Retention Test (BVRT) Score

    Time frame: Baseline and Day 30 (after intervention)

    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.

Sponsors and collaborators

Lead sponsor

Başakşehir Çam & Sakura City Hospital

Other Gov

Registry information

Official study title

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

Important dates

Study start
2022
Primary completion
2023
Study completion
2023
First posted
May 14, 2026
Registry last updated
May 14, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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