Therapeutic Effect and Mechanisms of Essential Oils in Mood Disorders: Interaction between the Nervous and Respiratory Systems

Abstract

Essential oils (EOs) are extracted from plants and contain active components with therapeutic effects. Evidence shows that various types of EOs have a wide range of health benefits. In our previous studies, the potential of lavender EO for prevention and even treatment of depression and anxiety symptoms was demonstrated. The favourable outcomes may be due to multiple mechanisms, including the regulation of monoamine level, the induction of neurotrophic factor expression, the regulation of the endocrine system and the promotion of neurogenesis. The molecules of EOs may reach the brain and exert an effect through two distinctive pathways, namely, the olfactory system and the respiratory system. After inhalation, the molecules of the EOs would either act directly on the olfactory mucosa or pass into the respiratory tract. These two delivery pathways suggest different underlying mechanisms of action. Different sets of responses would be triggered, such as increased neurogenesis, regulation of hormonal levels, activation of different brain regions, and alteration in blood biochemistry, which would ultimately affect both mood and emotion. In this review, we will discuss the clinical effects of EOs on mood regulation and emotional disturbances as well as the cellular and molecular mechanisms of action. Emphasis will be put on the interaction between the respiratory and central nervous system and the involved potential mechanisms. Further evidence is needed to support the use of EOs in the clinical treatment of mood disturbances. Exploration of the underlying mechanisms may provide insight into the future therapeutic use of EO components treatment of psychiatric and physical symptoms.

Effects of Shenxian Congee on Chronic Fatigue Syndrome Rats by NF-κB Signaling Pathway

“…Both oxidative stress and inflammation have an important role in the development of neurodegeneration. Reactive oxygen species triggers cellular apoptosis and pro-inflammatory signaling, which in turn produce undesirable repercussions that are supposed to be a possible cause of depression (Fung et al, 2021). Essential oils may be beneficial in depression due to their antioxidant and anti-inflammatory characteristics, based on the notion that ROS and inflammatory signaling play role in depression (Fung et al, 2021).…”

“…Reactive oxygen species triggers cellular apoptosis and pro-inflammatory signaling, which in turn produce undesirable repercussions that are supposed to be a possible cause of depression (Fung et al, 2021). Essential oils may be beneficial in depression due to their antioxidant and anti-inflammatory characteristics, based on the notion that ROS and inflammatory signaling play role in depression (Fung et al, 2021). Inflammation is associated with glucocorticoid resistance and reduced negative feedback of the HPA axis in response to high cortisol and cytokine levels (Mondelli et al, 2011).…”

Inhalation Aromatherapy via Brain-Targeted Nasal Delivery: Natural Volatiles or Essential Oils on Mood Disorders

“…Animal experiments have shown that inhalation of essential oils can prevent or relieve anxiety symptoms. These beneficial effects may result from modulation of monoamine levels, induction of neurotrophic factors expression, regulation of the endocrine system, and promotion of neurogenesis ( Fung et al, 2021 ). However, an animal experiment has shown that olfactory deficit induced by zinc (zinc gluconate + zinc acetate) did not impair the anxiolytic effects of lavender essential oil inhalation in the marble-burying test.…”

Beneficial effects of prolonged 2-phenylethyl alcohol inhalation on chronic distress-induced anxio-depressive-like phenotype in female mice

“…The first, allows the passage into the systemic blood circulation and then to the central nervous system by bypassing the blood-brain barrier. The second, importantly, displays strong anatomical connections with limbic regions known to exert a direct action on emotion [77]. Interestingly, it has been suggested that olfaction and depression display intricate relationships, since sensory deprivation often leads to depressive states, and reciprocally depressed patients frequently show olfactory impairments [78,79].…”