Essential oils from different species of "cedar" (Cedrus atlantica, C. deodara, Juniperus virginiana)

This article is a continuation of the article on cedarwood essential oil in support of ADHD.

Essential oils from various "cedar" species (Cedrus atlantica, C. deodara, Juniperus virginiana, etc.) mainly contain sesquiterpenes (himalalenes, cedrol, cedrenes, etc.) with sedative and nervous system-modulating potential. Existing preclinical studies indicate that the main components of these oils (e.g., cedrol) enhance parasympathetic activity and reduce sympathetic arousal, which in animal models translates into calming and anxiolytic effects. For example, cedrol inhalation in humans lowered heart rate and blood pressure and increased the high-frequency component of heart rate variability (indicating increased parasympathetic activity). Administration of cedrol to mice (i.p. 1200–1600 mg/kg) extended the time spent in the open arms of the elevated plus maze, indicating an anxiolytic effect, and altered neurotransmitter levels (increased 5-HT, decreased DA).

Cedrus atlantica oil in the form of a 10% balm reduced blood cortisol levels in stressed rats, which may indirectly alleviate excessive excitability.

In turn, Cedrus deodara oil improved spatial memory in old mice, suggesting an improvement in cognitive function. Overall, there are no direct clinical studies on ADHD/autism spectrum disorders, but there are indications that cedarwood oils may support relaxation, sleep, and regulate tension.

The best-studied species is Juniperus virginiana (Virginia cedar) – its cedrol-rich oil exhibits calming and anxiolytic effects in preclinical models. A strong sedative potential has also been demonstrated for Cedrus atlantica, although mainly in animal studies. For Cedrus deodara, evidence is scarce (mainly antioxidant effects and memory improvement in mice). In light of these studies, it is difficult to make therapeutic recommendations – cedarwood oils can be used as an adjunct to promote relaxation and sleep, but caution is advised in children (lower concentrations, dilutions).

Literature Search Methods

Scientific articles were searched (PubMed, Google Scholar, ScienceDirect) using the keywords: cedarwood essential oil ADHD, cedrol anxiolytic autism, Cedrus atlantica ADHD, juniperus cedarwood autism, cedar oil hyperactivity, etc. Works citing cedarwood oil components (e.g., cedrol, himachalene) and reports on the effect of aromatherapy on neurodevelopmental disorders were also checked. Priority was given to primary and peer-reviewed works. Example databases: PubMed, PMC, Semantic Scholar, ResearchGate, and official reports (NTP).

Cedarwood Oil Species and Their Chemical Composition

Oils called "cedarwood" come from both true cedars (genus Cedrus, Pinaceae) and junipers/cypresses (genus Juniperus, Cupressaceae). For example, Juniperus virginiana (Virginia cedar, also known as Western Red Cedar) contains sesquiterpenes: α-cedrene (20–35%), β-cedrene (4–8%), thujopsene (10–25%), cedrol (16–25%), and widdrol (2–5%). Oils from Cedrus atlantica (Atlas cedar) or Cedrus deodara (Himalayan cedar) are rich in himachalenes – mainly β-, α-, and γ-himachalene – which constitute a significant majority of the mass (e.g., ~30% β-himachalene). The presence of cedrol and cedrenes usually indicates oil from J. virginiana, while a high proportion of himachalenes suggests oil from Cedrus spp. (Atlantis or deodara). Manufacturer data (Latin name, CAS number) and chromatographic profile (e.g., cedrol vs. himachalene content) are also helpful in identifying the species.

Overview of Preclinical and Clinical Studies

Animal Studies (in vivo): Many experiments focused on the sedative and anxiolytic effects of cedarwood oil components. Kagawa et al. (2003) showed that inhaling pure cedrol in Wistar rats significantly inhibited motor activity and prolonged pentobarbital-induced sleep time – an effect also present in hypertension models (SHR) and ddY mice. Zhang et al. (2019) administered cedrol intraperitoneally (1200–1600 mg/kg) to female mice and observed an increase in entries into the open arms of the maze (EPM test) and prolonged time spent in the brightly lit chamber – indicating an anxiolytic effect. In these mice, brain 5-HT levels increased, and dopamine levels decreased (reduced 5-HIAA/5-HT ratio and increased DOPAC/DA), suggesting modulation of serotonergic and dopaminergic pathways.

Another model involves rodents subjected to chronic stress. Liosest et al. (2019) applied a 10% balm with Cedrus atlantica oil to the backs of rats subjected to daily forced swimming (a stressor). After 30 days, the treated group had significantly lower blood cortisol levels than both stressed rats without the oil and the control group. These results suggest that Atlas cedar aroma alleviated the stress response in rats. Furthermore, the effect of cedrol on the human nervous system was simulated – in a study by Dayawansa (2003), volunteers inhaled cedrol (approx. 14 μg/l), which significantly reduced heart rate and blood pressure and lowered the LF/HF component in HRV spectral analysis (sympathetic-parasympathetic coefficients). The researchers noted that inhaled cedrol increased parasympathetic activity and suppressed sympathetic activity, confirming the relaxing effect. The literature also mentions that cedarwood oil inhalation prolongs NREM sleep time in rats and reduces NREM sleep latency in humans.

In addition to sedation, cognitive functions were also studied: the Morris water maze showed that a chloroform extract from Cedrus deodara wood (100 mg/kg p.o.) accelerated learning and working memory in older mice. It is unclear whether the effect was mainly due to antioxidants or volatile terpenes. Notably, there is a lack of studies directly evaluating impulsive/hyperactive behavior in animals after cedarwood oils.

Clinical Studies (humans): There are no published RCTs or larger clinical studies evaluating cedarwood oils in ADHD or the autism spectrum in the available literature. There are press reports and preliminary reports (e.g., the mentioned unpublished "Friedmann study" with essential oils in ADHD), but without scientific verification. The few human studies mainly concern the effect of cedrol on the autonomic nervous system or sleep. Controlled studies evaluating concentration, impulsivity, or social functions in people with ADHD/autism have not been conducted. In practice, aromatherapists recommend Cedrus atlantica or J. virginiana oil for calming children, but this is based on clinical experience, not RCT results. In summary, there is no clinical evidence for an improvement in attention or a reduction in ADHD/autism symptoms by cedarwood oils; the current results are mainly subordinate to the mechanisms of sedation and relaxation.

Mechanisms of Action

The inhalation of cedarwood oils engages both the olfactory and neurovascular systems. The olfactory reflex directs scent molecules to the limbic system and hypothalamus – structures responsible for emotions and hormonal regulation. Simultaneously, volatile compounds pass into the lungs and then into the bloodstream, enabling a systemic effect. As a result, in people inhaling cedrol, an increase in vagus nerve activity (parasympathetic) and inhibition of sympathetic activity are observed, which translates into a reduced heart rate, blood pressure, and muscle tension.

At the molecular level, the primary target of cedrol is neurotransmitter modulation. Studies have shown that cedrol increases serotonin levels in the brain (by inhibiting reuptake or another mechanism) and simultaneously lowers dopamine. Such a shift in balance (increased 5-HT, decreased DA) is characteristic of an anxiolytic effect. There is no direct evidence of cedrol's effect on GABA or NMDA receptors in humans. Nevertheless, the sedative effect suggests an indirect effect that enhances GABAergic tone, analogous to other calming essential oils. Furthermore, studies indicate that cedarwood oils may stimulate the secretion of endocannabinoids or inhibit their breakdown (especially Juniperus virginiana), which can also modulate mood and excitability.

In summary, the mechanisms include the neural olfactory pathway (limbic/hypothalamic) and chemiotransmission in the brain (increased 5-HT, DA modulation, possible effect on the endocannabinoid system). These effects lead to reduced anxiety, calming, and facilitated sleep onset, which can indirectly positively affect ADHD/autism symptoms (e.g., better sleep, reduced irritability).

Safety and Pharmacokinetics

Cedarwood oils are generally considered safe when used properly. Technical toxicology reports from the NTP for Virginia cedarwood oils showed no significant toxicity at low concentrations; no carcinogenic or teratogenic effects were observed in animals. Concentrations used in cosmetics are usually below 5%, which is significantly lower than those used in toxicity tests. No sensitization or irritation has been observed with typical dilutions (e.g., 5–10% cedarwood oil in a base). However, it is worth noting that pure cedrol is a potent compound, so direct exposure to undiluted oil may cause skin or eye irritation in some individuals.

For children, cedarwood oils are usually recommended to be diluted to 1–2% (corresponding to 6–12 drops per 30 ml of carrier oil). In aromatherapy studies, half the adult dose is often used. Due to the sedative effect, undiluted oils should be avoided in young children, and inhalations should be supervised. Inhaling the oil (e.g., in a diffuser) usually does not cause such reactions and is preferred for sleep problems or tension. Since volatile components easily pass into the bloodstream, products containing cedarwood oil may cause drowsiness – it is therefore advisable to use them in the evening.

Pharmacokinetically, cedrol is rapidly absorbed through the lungs and mucous membranes after inhalation. It is metabolized in the liver and excreted in the urine. Its half-life has not been thoroughly studied, but inhalation effects are observed within a few minutes of exposure. Due to low volatility and the use of small concentrations, the risk of accumulation in the body is low.

Conflicts of interest: The available literature does not indicate industrial funding relevant to the discussed studies. The academic studies mentioned did not report conflicts of interest.

Comparison of Cedar Species (Table)

The table summarizes key differences: Virginian cedarwood oil has the most evidence for sedative effects, mainly due to cedrol. Cedrus species (Atlas and Deodara cedar) likely act similarly (due to himachalenes), but direct studies are lacking. No clinical study has confirmed the effect of cedarwood oils on ADHD or autism symptoms. In practice, aromatherapists use cedarwood oil as an additive to promote relaxation and better sleep, which can indirectly help hyperactive children (by reducing stress and improving sleep).

flowchart TD
  A[Exposure to essential oil: inhalation or skin application] --> B[Perception of scent and emotional reaction]
  A --> C[Absorption of volatile substances through lungs/skin]
  B --> D[Change in autonomic nervous system arousal (stress – relaxation)]
  C --> E[Interaction with neuroreceptors (e.g., GABA, NMDA, SERT, cholinergic receptors)]
  D --> F[Effects: sleep, muscle tension, mood]
  E --> G[Cognitive performance: attention, information processing]
  F --> H[Impact on daily functioning in ADHD/autism]
  G --> H

Conclusions and recommendations

Current evidence suggests that among cedarwood oils, Virginia cedar (Juniperus virginiana) has the greatest therapeutic potential – its oil, rich in cedrol, exhibits strong sedative and anxiolytic effects in animals. Cedrus species (Atlas and Deodara cedar) likely act similarly (due to himachalenes), but direct research is lacking. No clinical study has confirmed the effect of cedarwood oils on ADHD or autism symptoms. In practice, aromatherapists use cedarwood oil as an additive to promote relaxation and better sleep, which can indirectly help hyperactive children (by reducing stress and improving sleep).

Practical recommendations: If using cedarwood oil in children, choose a clearly identified species and preparation (e.g., Cedrus atlantica or Juniperus virginiana), preferably from a trusted manufacturer. It may be beneficial to use an essential oil diffuser in the evening (e.g., 3–6 drops in a diffuser) to aid sleep. For topical application, dilute the oil in a carrier oil (e.g., 1–2%). Avoid contact with eyes and mucous membranes. In case of doubt, consult an aromatherapist or doctor.

Search strategy: Databases used: PubMed, Google Scholar, Semantic Scholar, ScienceDirect. Example queries: “cedarwood oil ADHD study”, “cedrol anxiety mice”, “Cedrus atlantica memory”, “Juniperus virginiana autonomic cedarwood”, “aromatherapy autism clinical trial”. Cited works and peripheral reports (ISO standards, toxicological reports, cosmetic ingredient databases) were also searched.

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