Bergamot and alertness: what one well-designed study showed.

Of the citrus oils used in aromatherapy research, bergamot has the most consistent evidence base for mood and stress effects. One study in particular — the 2015 Watanabe et al. trial¹ — stands out for its design quality and its measured outcomes.

What the researchers did

Forty-one healthy women participated in a randomized crossover trial. Each participant went through two conditions in different sessions: bergamot oil inhalation and a water control. The sessions were separated by a washout period. Outcomes were measured on two tracks simultaneously: physiological (salivary cortisol, skin temperature, pulse rate) and subjective (mood scales).

The bergamot used in the study was standardized bergapten-free oil — a detail that matters for generalization, because bergapten (a furanocoumarin in bergamot) is removed from many commercial oils due to its photosensitizing properties. The oil used in the study is closer to what consumer products use.

What the researchers found

Two findings, both significant.

First, salivary cortisol dropped measurably in the bergamot condition compared to control. Cortisol is a measurable biomarker for stress response, and the reduction was statistically significant. This is one of the few aromatherapy studies that finds a physiological stress marker — not just a self-reported feeling — responding to an inhaled oil.

Second, mood scores improved. Participants reported better feelings on standardized mood scales in the bergamot condition. The mood improvement tracked with, but was not entirely explained by, the cortisol change.

What the study did not claim

Forty-one participants is a small sample. The crossover design controls for individual variation, which strengthens the internal validity, but the study is a single trial and has not been replicated at scale. The Watanabe paper did not claim that bergamot reduces clinical anxiety or treats stress disorders.

The study also measured acute effects — the bergamot and control sessions were single exposures. Long-term effects, or the effects of repeated daily exposure from a candle, were not measured.

Why the study matters

The salivary cortisol finding is the most cited result from this paper, and for good reason. Cortisol is an objective measure. Finding a reduction in an objective stress biomarker after aromatherapy exposure is uncommon in this literature, which leans heavily on self-report. When an objective measure and a subjective measure move in the same direction in the same trial, that is a stronger signal than either alone.

The 2017 Han et al. pilot study² — set in a mental health treatment center waiting room, an ecologically stressful environment — replicated the improved mood finding in a real-world setting rather than a controlled lab.

We chose bergamot for the Morning Ritual because of the Watanabe cortisol finding and the alertness and mood trajectory. Mornings carry their own quiet stress; bergamot is the ingredient in the blend with the clearest physiological evidence for stress reduction. That is what we mean when we say our formulation choices have reasoning.