The Wyart Study: Androstadienone Effects on Women's Mood and Cortisol

Overview

The 2007 study by Claire Wyart and colleagues at UC Berkeley, published in the Journal of Neuroscience, represents one of the most robust demonstrations of human chemosensory communication. It showed that merely smelling androstadienone, a component of male sweat, causes measurable changes in women’s cortisol levels and mood.

This study is frequently cited as evidence that humans respond to chemical signals from other humans, though what exactly this means for the “pheromone” debate remains nuanced.

Study Details

Citation

Wyart C, Webster WW, Chen JH, Wilson SR, McClary A, Khan RM, Sobel N. (2007) “Smelling a Single Component of Male Sweat Alters Levels of Cortisol in Women.” Journal of Neuroscience 27(6):1261-1265. DOI: 10.1523/JNEUROSCI.4430-06.2007

Research Team

The study was conducted at the Helen Wills Neuroscience Institute at UC Berkeley, led by Noam Sobel, a leading researcher in human olfaction and chemosensation.

The Compound Tested

Androstadienone (4,16-androstadien-3-one):

• A 16-androstene steroid derived from testosterone
• Found at higher concentrations in male sweat
• Previously proposed as a “putative human pheromone”
• Has been shown to activate hypothalamic regions in women’s brains

Methodology

Study Design

• Participants: 48 female undergraduate students
• Design: Double-blind, placebo-controlled, within-subject
• Exposure method: Sniffing (no skin contact)
• Control: Yeast compound with similar odor character

Exposure Protocol

Participants smelled:

• Either androstadienone dissolved in propylene glycol
• Or a control odor (yeast-derived compound)

The key innovation was that exposure occurred via sniffing alone, with no direct skin contact. Participants took 20 sniffs of the compound, mimicking natural exposure conditions.

Measurements

1. Salivary cortisol: Collected before and at multiple timepoints after exposure
2. Mood assessments: Standardized questionnaires
3. Physiological arousal: Heart rate, skin conductance
4. Sexual arousal: Self-report measures

Controls for Confounds

The researchers controlled for:

• Menstrual cycle phase
• Time of day (cortisol has diurnal rhythm)
• Odor intensity matching between androstadienone and control
• Subject awareness of what they were smelling

Key Findings

Finding 1: Cortisol Maintenance

The headline finding: Women who smelled androstadienone maintained significantly higher cortisol levels compared to those who smelled the control odor.

Condition	Cortisol Pattern
Control odor	Normal decline over session
Androstadienone	Maintained at elevated levels

The effect:

• Began within 15 minutes of exposure
• Persisted for approximately 1 hour
• Was statistically robust (p < 0.05)

Important nuance: Androstadienone didn’t increase cortisol; it maintained levels that would otherwise decline during a laboratory session. The control group showed the normal cortisol decrease expected when sitting quietly.

Finding 2: Mood Enhancement

Women exposed to androstadienone reported:

• Increased positive mood over the session
• Enhanced physiological arousal
• Increased sexual arousal with longer exposure
• These effects grew stronger with continued exposure

Finding 3: No Skin Contact Required

Unlike some previous studies that applied compounds directly under the nose, this study showed effects from sniffing alone. This is significant because:

• It resembles natural exposure conditions
• Rules out absorption through skin
• Confirms olfactory pathway involvement

What This Study Proves

Definitively Established

1. Single compound effect: Androstadienone alone, not a complex mixture, produces measurable effects

2. Hormonal response: Human physiology (specifically HPA axis/cortisol) responds to chemosignals from conspecifics

3. Olfactory mediation: Effects occur through smelling, not skin absorption

4. Sex-specific effects: The study tested only women; effects may be sex-specific

5. Unconscious processing: Effects occurred regardless of whether participants could consciously identify the odor

What It Suggests (But Doesn’t Prove)

1. Pheromone-like function: Androstadienone may serve as a human chemosignal, though it doesn’t meet strict pheromone criteria

2. Adaptive function: Cortisol maintenance might have functional significance (stress modulation? heightened vigilance? social signaling?)

3. Male-to-female communication: Since androstadienone is higher in male sweat, this could represent chemical communication from men to women

What This Study Does NOT Prove

Common Misinterpretations

1. “Androstadienone is a human pheromone”

   • The study authors use “putative pheromone” cautiously
   • Effects are subtle, not stereotyped behavioral responses
   • Individual variation exists

2. “Androstadienone makes women attracted to men”

   • The study measured cortisol and mood, not attraction
   • Sexual arousal increased but wasn’t the primary finding
   • No measure of behavioral change toward actual men

3. “Pheromone products will have these effects”

   • Study used pure, controlled concentrations
   • Commercial products vary widely in composition
   • Dosing and delivery methods differ

4. “Effects are universal”

   • Study showed average effects; individual variation exists
   • Some women may not respond
   • Context matters

The Cortisol Question

Why Does Cortisol Matter?

Cortisol is often called the “stress hormone,” but this is oversimplified. Cortisol:

• Is part of the body’s arousal system
• Increases alertness and attention
• Mobilizes energy resources
• Has complex effects on mood (not simply negative)

Interpreting the Cortisol Effect

The maintained cortisol could represent:

1. Heightened alertness: Preparing for social interaction
2. Attention modulation: Enhanced focus on the social environment
3. Stress response: Though mood data don’t support this interpretation
4. Arousal: General physiological activation

The accompanying positive mood suggests this isn’t a stress response in the negative sense. Rather, it may represent a state of alert engagement.

Replication and Extension

Supporting Studies

Several other studies support the Wyart findings:

Jacob et al. (2001): Earlier work showed androstadienone affects mood and autonomic measures in women, with effects dependent on social context (male vs. female experimenter present).

Bensafi et al. (2004): Demonstrated dose-dependent mood effects of androstadienone in women, with higher doses producing stronger positive mood shifts.

Savic et al. (2005): PET imaging showed androstadienone activates hypothalamic regions in women but not heterosexual men, providing a neural substrate for the hormonal effects.

Critiques and Limitations

Sample characteristics: University undergraduates may not represent all women.

Laboratory setting: Effects in controlled settings may differ from real-world social situations.

Acute exposure: Long-term or repeated exposure effects are unknown.

Male response unknown: The study only tested women; effects on men remain unclear from this study.

Practical Implications

For Understanding Pheromones

The Wyart study is often cited as the strongest evidence that humans engage in chemosensory communication. However, users should understand:

1. Effects are subtle and physiological, not dramatic behavioral changes
2. Androstadienone likely works alongside other cues, not instead of them
3. Context matters: The social setting influences outcomes
4. Individual variation means not everyone responds equally

For Pheromone Product Users

If you use products containing androstadienone:

1. Don’t expect dramatic effects: The study showed mood and cortisol changes, not instant attraction
2. Consider the context: Effects may be stronger in social settings
3. Target female interactions: The study specifically tested effects on women
4. Subtle is expected: Physiological priming, not overwhelming responses

Key Takeaways

1. Landmark study: First to show a single sweat component affects women’s hormones
2. Robust methodology: Double-blind, placebo-controlled, within-subject design
3. Cortisol maintenance: Androstadienone prevented normal cortisol decline
4. Mood enhancement: Positive mood increased with exposure
5. Natural exposure: Effects occurred from sniffing, not skin contact
6. Cautious interpretation: Evidence for chemosignaling, not proof of “pheromones”
7. Real but subtle: Effects are measurable but not dramatic
8. Context-dependent: Social setting likely influences outcomes

Scientific Confidence

Confidence Level: High

The Wyart study is methodologically sound and has been supported by subsequent research. The finding that androstadienone affects cortisol in women is well-established. However, the practical significance and real-world implications require more cautious interpretation.

The Bottom Line

The Wyart study demonstrates that humans can influence each other’s hormonal state through smell. A single compound in male sweat, androstadienone, maintains elevated cortisol levels in women and enhances positive mood. This is strong evidence for human chemosensory communication.

However, this doesn’t prove that commercial pheromone products work as advertised, that effects are universal, or that androstadienone will make you more attractive. What it does prove is that the basic mechanism, chemical communication between humans, is real and measurable.