A 30-year-old trader sitting down at his desk this morning has, on average, roughly 25% less testosterone circulating in his body than a 30-year-old trader had in 1999. That is not a lifestyle anecdote or a gym-bro talking point. It is a measured, population-level finding, and it matters for testosterone and trading performance because testosterone is one of the only biological variables ever shown, in a live market, to predict how much money a trader makes on a given day.
What Does Testosterone Have to Do With Trading Performance?
A trader’s testosterone level each morning has been shown, in a real trading environment, to predict how profitable he is by the end of the day.
The clearest evidence comes from John Coates, a former Goldman Sachs and Deutsche Bank derivatives trader who left Wall Street to study the biology of risk-taking at Cambridge. Working with neuroscientist Joe Herbert, Coates recruited 17 male traders on a London derivatives floor and sampled their saliva twice a day, at 11am and 4pm, over eight consecutive trading days, tracking testosterone and cortisol alongside each trader’s live profit and loss (Coates & Herbert, 2008, PNAS).
The result: on mornings when a trader’s testosterone was above his own median for the study, he went on to make significantly more money for the rest of the day than on low-testosterone mornings. Fourteen of the seventeen traders showed the pattern, the effect size was large (Cohen’s d = 0.97), and because the high-testosterone days were different for each individual trader, the result could not be explained away by a strong market day lifting everyone’s hormones at once. Testosterone predicted the trader, not the market.
One detail is easy to miss: the traders in that study were young. Their average age was 27.6, with a range of 18 to 38, almost exactly the cohort now showing the steepest documented drop in baseline testosterone. The population this research describes is the same population now starting the trading day with less of the hormone the research says matters.
Why Are Young Men’s Testosterone Levels Falling?
Average testosterone in American men under 40 has dropped roughly 25% since 1999, and the decline tracks birth year, not just age.
The most cited data point comes from a study of 4,045 men aged 15 to 39 using the CDC’s National Health and Nutrition Examination Survey (NHANES). Comparing 1999-2000 to 2015-2016, mean total testosterone fell from 605.39 ng/dL to 451.22 ng/dL, a decline of about 25% (p < 0.001), and the drop held even among men with a normal BMI (Lokeshwar et al., 2021, European Urology Focus). Roughly 20% of adolescent and young adult men in the study now meet the clinical criteria for testosterone deficiency.
This isn’t an isolated finding. A comprehensive January 2026 review pulled together the wider evidence: an age-independent decline of roughly 0.5 to 1.0% per year across multiple populations, a Massachusetts cohort tracked from the late 1980s through 2004 showing a similar age-independent drop that couldn’t be explained by lifestyle changes researchers could measure (Travison et al., 2007, Journal of Clinical Endocrinology & Metabolism), a U.S. Air Force veterans cohort that lost 33% of its average testosterone between 1982 and 2002, and large national cohorts in Finland and Israel confirming the same generational pattern (Fraile-Martínez et al., 2026, International Journal of Molecular Sciences). No comparable decline has been documented in women, which points to something specific happening to men.
The likely causes are a mix of the obvious and the underappreciated: rising obesity, more sedentary desk-based work, ultra-processed diets, chronic psychological stress, and exposure to endocrine-disrupting chemicals in plastics and packaging. Sleep is in that list too. Just one week of nights capped at five hours can cut testosterone by 10 to 15%. If sleep, cortisol, and the nervous-system side of this topic are new territory for you, How Sleep, Hormones and Lifestyle Are Affecting Your Trading covers that ground in depth. This article focuses on the piece that post doesn’t: the fact that baseline testosterone itself has been sliding for a generation, independent of any single trader’s sleep habits.
What Is the “Winner Effect,” and Why Does It Cut Both Ways for Traders?
Winning raises testosterone, which raises confidence and risk appetite, which raises the odds of winning again, until the same mechanism pushes a trader into worse and worse risk-reward trades.
The winner effect was first documented in animals: a competitor that wins one contest shows a rise in testosterone, becomes more confident and more willing to fight, and is measurably more likely to win the next round too (Coates & Herbert, 2008). Coates and Herbert applied the same model to financial markets and found it held. Traders on a winning streak showed testosterone rises alongside their gains, and that androgenic lift tracked with increased risk-taking on subsequent trades.
In his own words, describing the research behind The Hour Between Dog and Wolf: “You feel this narcotic effect when you’re making a lot of money and expecting a large bonus, and that shifts your preference for risk. You start taking much more risk with worsening risk-reward trade-offs, and you eventually blow up” (Cambridge Judge Business School).
“Rising levels of testosterone in young male traders, when they’re on a winning streak, are actually shifting their risk preferences and causing them to take too much risk.”John Coates, Cambridge Judge Business School
That is the mechanism underneath a pattern most traders recognize from the inside: three great days, then a fourth day that gives half of it back. It’s also the biological layer underneath what shows up, from the outside, as breaking your own trading rules or slipping into overtrading right after a hot streak, not right after a loss. In separate laboratory research cited in the same paper, administering testosterone to subjects playing a card-based risk task caused them to prefer high-variance, negative-expected-value choices over safer, positive-expected-value ones. Confidence past a certain point stops being an asset.
Why Did Coates Call His Book “The Hour Between Dog and Wolf”?
It’s a centuries-old expression for twilight, the moment you can’t tell whether what’s emerging from the tree line is a tame dog or a wild wolf, used as a metaphor for the moment a trader’s own biology tips them from disciplined into reckless.
The phrase dates back to around 200 AD in Latin and was common in medieval French. It describes the ambiguous hour of dusk, when the light is too uncertain to tell a dog from a wolf, and when people once believed a tame animal could transform into a wild one. Coates uses it as a metaphor for what he found in his research: traders don’t consciously decide to become reckless. Something shifts underneath conscious awareness, in the hour between one state and the other, and by the time it’s visible from outside, the transformation has already happened.
Coates is explicit that this isn’t a story about weak discipline. It’s a rejection of the idea that mind and body operate separately in the first place. “Body and brain evolve together,” he has said of the research. “When we take risks, body and brain are collaborating as a single unit” (Cambridge Judge Business School). Most traditional trading psychology treats the mind as something that runs independently of the body it’s attached to. Coates’ research, and the testosterone data underneath it, says otherwise.
What About Cortisol? Doesn’t Stress Affect Trading Too?
While testosterone may encourage greater risk-taking, sustained cortisol can pull traders in the other direction. It appears to track market uncertainty more closely than losses themselves, and may push traders toward excessive caution just when volatility is creating both heightened risk and opportunity.
In the same Cambridge study, cortisol did not rise simply because traders lost money. Instead, it rose with the variance of their returns and, even more strongly, with the market’s implied volatility. The relationship was remarkably strong: as market volatility rose and fell, the traders’ cortisol levels closely followed it (R² = 0.86).
In the short term, the stress response can heighten alertness and focus. But when cortisol remains elevated, it may increase risk aversion and impair a trader’s ability to evaluate opportunity rationally. The researchers proposed a compelling possibility: just as testosterone-fueled risk-taking may help inflate a bull market into a bubble, sustained cortisol and collective risk aversion may deepen a bear market into a crash.
This piece focuses specifically on testosterone because that is the side of the story connected to the generational decline. For the fuller picture, including cortisol, sleep architecture, and the nervous-system mechanics of trading stress, see How Sleep, Hormones and Lifestyle Are Affecting Your Trading.
Should Traders Actually Get Their Hormones Tested?
If you want to know whether biology is shaping your trading instead of guessing, the only way to find out is to measure it.
Here’s the reframe worth sitting with: a lower testosterone reading isn’t evidence that something is wrong with you. It’s information. The traders who struggle most with hesitation, inconsistency, or a pattern of giving back a winning streak often assume the problem is a discipline problem, something to white-knuckle through with more willpower. Sometimes it is. Sometimes it’s biology creating headwinds that no amount of journaling or rule-following will fully overcome on its own. You can’t tell the difference without data.
That’s the thinking behind The Wall Street Coach‘s partnership with Marek Health, a functional medicine lab-testing platform. It exists for traders who want an honest answer to a specific question: is my biology working with me or against me right now?
What Is the Wall Street Coach x Marek Health Partnership?
A partnership giving Kim’s clients guided access to comprehensive hormone and biomarker testing, interpreted by a Marek Health coach rather than left as a spreadsheet of numbers to decode alone.
Marek Health offers two testing tiers through the partnership. Both go well beyond a standard annual physical, which typically tests only TSH for thyroid function and often skips a full sex-hormone panel entirely.
| What’s covered | Lab Package | Ultimate PackageMost comprehensive |
|---|---|---|
| Biomarkers tested | 82 | 100+ |
| Number of tests | 27 | 33 |
| Sex hormones | Total & free testosterone (uncapped), estradiol, SHBG, progesterone, prolactin, cortisol, DHEA-S | Same, plus pregnenolone |
| Thyroid panel | TSH, Free T3, Free T4, TPO antibodies | Adds Reverse T3 and additional thyroid antibody testing (TgAb) |
| Cardiovascular / lipids | Standard lipid panel, ApoB | Adds homocysteine |
| 45-minute coach review call | Included | Included |
| Licensed medical provider consult | Separate step, not included in panel price | Separate step, not included in panel price |
Both packages include a detailed report and a 45-minute review with a Marek Health coach, helping clients understand their results in the context of their health history, symptoms, and goals. Comparable comprehensive testing can cost hundreds to more than a thousand dollars out of pocket, depending on the laboratory, the specific biomarkers ordered, and whether professional interpretation is included. The distinction here is not simply the number of tests. It is having those results organized, interpreted, and translated into practical next steps rather than receiving a spreadsheet of numbers without meaningful guidance.
“Marek has been helping guide my health and vitality for a year, and I’m consistently impressed with every facet of their service. The transformation in my health, energy, and vitality has been profound, and quite positively impacted my personal well-being, family, business, and the inevitable challenges along the way.”John I., Verified Client
How Does the Marek Health Process Work?
Four steps: order your labs with Kim’s partner code, get your blood drawn locally, review the results on a call with a Marek Health coach, then get ongoing support.
Step 1: Order Your Labs
Using the partner code Kim provides, you fill out a short health history questionnaire and receive a lab requisition by email within 24 business hours. You take that form to a diagnostic center near you for a standard blood draw. Results typically arrive within 7 to 14 days.
Step 2: Your Review and Recommendations
You meet by video call with a Marek Health coach, who walks through your full lab report, explains what each biomarker means, and connects the dots between your results and the physical, mental, and sexual health goals you actually care about.
Step 3: Medical Provider Consult (optional)
If your results point toward something worth treating, a licensed partnered provider can meet with you to build a customized treatment plan, with any prescribed treatments shipped directly to you.
Step 4: Ongoing Support
Monthly check-ins with your health team keep the process from being a one-time snapshot, so you can track whether the changes you’re making are actually moving your numbers.
See What Your Own Biology Is Doing to Your Trading
Kim provides her Marek Health partner code directly to coaching clients, along with guidance on which panel makes sense for where you are. Book a call to get started.
Book a Call With KimFrequently Asked Questions
Does testosterone actually affect trading performance?
It appears to. In a field study of 17 male London derivatives traders, higher morning testosterone significantly predicted greater profitability during the remainder of that trading day, with a large observed effect size (Cohen’s d = 0.97). Because each trader’s high-testosterone days occurred on different dates, the researchers concluded that general market movements were unlikely to explain the relationship (Coates & Herbert, 2008).
What is the “winner effect” in trading?
The winner effect describes a feedback loop first documented in athletes and competing animals: winning raises testosterone, which can increase confidence and risk appetite, raising the odds of winning again. Applied to trading, a profitable streak may raise testosterone and push a trader toward progressively larger, lower-quality risk-reward trades until the streak reverses.
Why are testosterone levels falling in young men?
NHANES data on more than 4,000 American men aged 15 to 39 showed that average total testosterone fell roughly 25% between 1999 and 2016, independent of age (Lokeshwar et al., 2021). Researchers have proposed a combination of possible contributors, including rising obesity, sedentary lifestyles, ultra-processed diets, chronic psychological stress, poor sleep, and exposure to endocrine-disrupting chemicals such as BPA and phthalates.
Is the testosterone decline just about obesity?
No. The decline persists even among men with normal BMI, and a 20-year cohort study found that men who maintained or lost weight still experienced an average testosterone decline of roughly 19% (Mazur et al., 2013). Obesity is a contributing factor, not the whole explanation.
What does cortisol do to a trader’s risk-taking?
Where testosterone tracks with wins and tends to raise risk appetite, cortisol tracks with uncertainty and volatility and may increase risk aversion when it remains elevated. In the same Cambridge field study, cortisol levels correlated strongly with market-implied volatility (R² = 0.86). The researchers proposed that sustained cortisol elevation could make traders overly cautious at exactly the moments volatility creates opportunity.
What’s included in a Marek Health lab panel?
The Wall Street Coach x Marek Health partnership offers two tiers: a Lab Package covering 82 biomarkers across 27 tests, and an Ultimate Package covering 100+ biomarkers across 33 tests. Both include comprehensive sex hormone testing (total and free testosterone, estradiol, SHBG), thyroid function, cortisol, metabolic and lipid panels, plus a 45-minute review call with a Marek Health coach who benchmarks your results against optimal ranges, not just the standard “normal” reference range.
How do I access the Wall Street Coach’s Marek Health partnership?
Kim provides her partner access code directly to clients. Book a call to get the code and guidance on which panel fits your situation.
Can low testosterone be treated?
Kim is not a doctor and does not prescribe or diagnose. The Marek Health partnership connects traders to licensed clinicians who can review lab results and, where appropriate, build a customized treatment plan. Kim’s role is to help traders understand how their biology may be interacting with their trading patterns, then refer out for medical care.
About the Author
Kim Ann Curtin, known as The Wall Street Coach™, is a trading psychology and performance coach who works at the intersection of decision-making and the nervous system. For over 20 years, she has worked with institutional traders, hedge funds, and senior executives. Her clients include traders and executives affiliated with firms such as GIC, Morgan Stanley, Bank of America, King Street Capital, BC Partners, and Blackstone, along with leading trading communities including Investors Underground, Bear Bull Traders, True Trader, and StocksToTrade. She has also coached traders and leadership teams at CenterPoint Securities prior to its transition to Clear Street. She is the author of Transforming Wall Street and host of The Wall Street Coach Podcast (110+ episodes), focused on helping traders perform at a high level when it matters most. Book a consultation.