By acting on the olfactory system through the aroma molecules of specific plant essential oils, scented candles can indirectly influence the limbic system of the brain (the area that controls emotions and memory), thereby relieving stress, improving sleep, enhancing concentration, and so on. Here are the specific correlations and scientific basis: 
How do scented candles affect mental health? 
Principle of Action 
The direct connection between the sense of smell and the brain: 
Odor molecules stimulate the olfactory nerves through the nasal cavity and directly transmit to the amygdala (emotional center) and the hippocampus (memory center) in the brain, quickly triggering emotional responses. 
Physiological effects: 
Certain essential oil components (such as linalool and limonene) can regulate the levels of stress hormones (such as cortisol) through the bloodstream or the nervous system. 
Common Psychological Benefits of Essential Oils 
Essential oil type  Psychological effect  Suitable scenarios 
Lavender: Reduces anxiety and promotes sleep. Use before bedtime or when feeling stressed. 
Sweet orange / Bergamot: Boosts mood, reduces depression. Morning, period of low spirits. 
Cedar/Boswellia - Enhances sense of security, stabilizes mind. Suitable for meditation and focused work. 
Mint / Rosemary Boosts alertness, enhances concentration. Useful when studying or feeling tired. 
Yilan Yilan: Relieves tension, promotes relaxation. Bathing, creating a romantic atmosphere. 
2. Support for Scientific Research 
Lavender and Sleep: 
Multiple studies have shown that the aroma of lavender can lower heart rate and promote deep sleep (Journal of Evidence-Based Complementary Medicine). 
Citrus fruits and emotions: 
Sweet orange essential oil has been proven to reduce anxiety (Journal of Alternative Medicine). 
Sandalwood and Meditation: 
The scent of sandalwood can activate the prefrontal cortex of the brain, helping one enter a meditative state (Journal of Chemical Senses). 
3. How to maximize psychological benefits? 
Using Techniques 
Time Control: 
Light a lavender candle 30 minutes before bedtime (keep it burning for 20-30 minutes; avoid over-reliance). 
Environmental Compatibility: 
Combine with soft lighting, gentle music or deep breathing exercises to enhance the relaxation effect. 
Personalized Choices: 
Adjust the fragrance according to your own emotional state (for example, choose a soothing chamomile fragrance before menstruation). 
Notes for Attention

Avoid inferior scented candles (which may contain volatile benzene compounds and could actually irritate the nerves). 
Patients with depression or severe anxiety should receive professional treatment and should not rely solely on aromatherapy. 
4. Alternatives and Supplements 
Fireless aromatherapy: The rattan diffuser is suitable for people who are sensitive to open flames. 
Compound formula: Mix 2-3 types of essential oils (such as lavender + cedar) to enhance the effect. 
5. User Feedback Case 
Insomnia improvement: Many people have reported that using lavender-scented essential oil candles before bedtime shortens the time it takes to fall asleep. 
Work concentration: The combination of mint and rosemary can help remote workers stay alert. 
Scented candles, as an auxiliary tool, can create a safe and comfortable psychological environment through their fragrance. However, they should be used in conjunction with a healthy lifestyle and mindfulness habits.