Whether it's the aroma from freshly baked muffins, the scent of a particular perfume or the smell of grass after rainfall – we all recognize that our sense of smell can have a powerful impact on our emotions, mood and can even trigger memories.
It is this connection that is harnessed in the science of aromatherapy. In fact, it has been utilized for centuries dating as far back as the ancient civilizations of Egypt, India and China, where essential oils were first used.
Fortunately, essential oils have made a resurgence in the mainstream, and are now popular not only among aromatherapists and holistic practitioners, but also for individual use at home. Given their safety, effectiveness and ease of use, they are a great tool for anyone suffering from anxiety and other mental health issues such as stress and depression.
How Do Essential Oils Work?
Essential oils are highly concentrated plant extracts that contain healing properties. They operate through two main systems in the body: 1) the olfactory system, which regulates our sense of smell; and 2) the limbic system, which regulates emotions, memories and arousal. These two systems are connected by the olfactory bulb in the forebrain.
When a scent is inhaled, the molecules travel up the nasal cavity and bind to receptors in the olfactory bulb. This extends into the limbic system, which contains the amygdala – the emotional centre of the brain that governs primal emotions such as fear, anger and worry. Once the scent reaches this point, it helps initiate calming responses.
A 2008 study shows this mechanism in action; subjects with terminal cancer were either given a regular hand massage, or an aroma hand massage that used a mixture of three essential oils: lavender, bergamot and frankincense. Results showed the aroma hand massage was significantly better at reducing pain and depression. 
The Best Essential Oils for Anxiety
Essential oils have been used for psychological issues such as stress and anxiety for centuries, however it is more recently that modern science is starting to dig deeper and investigate their healing properties.
While more research is still to be done, below is a curated list of essential oils that have been verified by clinical research:
A 2017 trial measured the impact of geranium oil on anxiety in patients who had recently suffered a heart attack. On the second day of admission, three drops of geranium essential oil, or placebo, were poured on absorbing patches attached inside patients' oxygen mask. Patients were asked to inhale the aroma for 20 minutes a day on two consecutive days.
There was a significant difference in anxiety scores, with the geranium aroma group outperforming the placebo. 
Another 2015 study further validates this research; scientists found that inhaling geranium essential oil significantly reduced childbirth anxiety for women during the first phase of labour, as compared to a placebo. 
A 2014 pilot trial revealed that inhalation of ylang ylang resulted in a significant improvement in self-esteem . Another 2006 study done in Korea concluded that ylang ylang, when blended together with lavender and bergamot, was able to reduce blood pressure and also levels of the stress hormone, cortisol. 
This is traditionally used as a nervous system tonic and is associated with calmness, stability and grounding. A study published in Natural Product Research showed that vetiver was able to lower anxiety in rats, however further research is still required to validate this in humans as well. 
This is perhaps one of the most popular essential oils for relaxation and calming the nervous system. According to a systemic review of essential oils, lavender has sedative and narcotic actions, which is what makes it an excellent choice for improving sleep quality. 
While some research exists in relation to anxiety, more still needs to be done. One 2014 study revealed that lavender essential oil was able to reduce dental patient anxiety , however another 2014 study indicated that lavender essential oil did not have a significant effect on anxiety in patients after coronary artery bypass surgery. 
Till date, research has shown that bergamot helps reduces anxiety in rats  . While more human trials need to be done, a small pilot trial in 2017 showed that the inhalation of bergamot essential oil improved positive feelings in patients at a mental health treatment centre . Another 2015 has also shown that inhalation of bergamot essential oil and water vapour, combined with rest can reduce anxiety, fatigue and improve mood. 
How To Use Essential Oils for Anxiety
When getting started with essential oils for anxiety, it's advised use an anti-anxiety blend. Essential oils work best when used synergistically, and this is also a more cost effective option as opposed to purchasing separate bottles.
For example, the Veeva anxiety blend has been handcrafted by aromatherapists and contains geranium, ylang ylang, vetiver, frankincense, and lime.
Once you have your essential oil blend for anxiety, there are multiple ways to use it. Below are some suggestions:
Diffuser or nebulizer – both of these tools help disperse the aroma of essential oils into the air; a diffuser uses evaporated air, and a nebulizer uses gas particles. The latter is slightly more effective and absorbable. Simply place a few drops of essential oil into the provided compartment. Keep them in your bedroom or living room.
Diffuser reeds – this is a more primal version of a diffuser. Simply purchase wooden reeds and place them inside an essential oil bottle; the scent travels through the reeds and will spread throughout the room.
Aromatherapy roll-ons – keep a roll-on in your desk drawer, purse, pocket, or rally anywhere. Roll onto your pulse points daily or when feeling anxious.
Beauty products – add a few drops into homemade beauty products, or unscented products such as lotion, body butter and hand cream
Bath – add a few drops to your bath to help unwind at night
Direct inhalation – keep a bottle within reach, and inhale when required
Indirect application – place a few drops onto your pillow or blanket at night to quieten your mind and help you sleep