Skip to main content

Daily Hormone Fluctuations Drive Risk and Fear

SimSearch is BigShort's daily performance prediction graph, generated dynamically each day. SimSearch and other BigShort indicators work because human decision making and performance are strongly influenced by hormones in predictable ways. This fact drives patterns in human reaction to various scenarios, which give rise to stock market patterns.

Below we've gathered and summarized the research so you can up your trading results in no time.

Research suggests traders' hormone levels swing throughout the day, influencing everything from aggression and confidence to fear and risk aversion. Early-morning spikes of testosterone and cortisol can fuel bold moves or anxious selloffs, while mid-day lulls and late-day surges in other brain chemicals may nudge traders between caution and impulsivity. By mapping these physiological patterns, day and swing traders may gain an edge — or at least avoid being blindsided by their own biology.

TESTOSTERONE: Fuel for Morning Confidence and Risk​

Let's start with the "confidence hormone." Testosterone tends to peak in the early morning. Researchers such as Coates and Herbert have noted, "Testosterone in male athletes… will rise prior to a competition and rise even further in a winning athlete," a phenomenon they call the "winner effect." In financial contexts, the same pattern appears: "Daily testosterone levels were significantly higher on days when traders made more than their one-month daily average than on other days."

This hormonal surge can improve performance short-term by boosting confidence, but too much testosterone may prompt excessive risk-taking. Morning markets often see big bursts of trading volume and volatility. Part of that is habit and market structure, but biology may also play a role.

CORTISOL: Stress Hormone Behind Fear and Caution​

Cortisol is the body's main stress hormone — it soars in moments of uncertainty or threat. A field study of London traders found cortisol levels rose 68% over a two-week period of high market volatility. Over time, elevated cortisol breeds caution, anxiety, and risk aversion.

In one experiment, participants given cortisol over several days to mimic chronic stress showed "a dramatic drop in participants' willingness to take risks, with the 'risk premium'… falling by 44%." This explains why a string of losses or prolonged market chaos can make traders sell prematurely or avoid opportunities.

DOPAMINE: Reward Rushes and Impulsive Trades​

Dopamine is the brain's "reward" neurotransmitter, surging when we anticipate or receive something pleasant — it's the rush you get before clicking "buy" on a promising trade. Research has linked extreme highs or lows in dopamine activity to erratic risk-taking behavior.

While dopamine can energize a trader to seize an opportunity, it's also behind gambling-like behavior. After a big win, dopamine spikes can lure traders into doubling down or chasing the same thrill.

SEROTONIN: Mood, Patience, and Logic Under Pressure​

Serotonin stabilizes mood, curbs impulsivity, and promotes a sense of well-being. In a famous neuroscience experiment, lowering serotonin in monkeys "decreased preference for the safe option in a gambling task," making them impulsive risk-takers.

Traders low on sleep or proper nutrition likely have dips in serotonin, which may explain those days when everything feels irritating or rushed. By contrast, healthy serotonin levels align with calmer, more deliberative behavior: you weigh pros and cons, follow the trading plan, and avoid revenge-trading after a loss.

Daily Rhythms and Trading Patterns​

Our hormones don't stand still; they follow natural circadian rhythms. Cortisol typically spikes shortly after waking, then tapers off by midday. Testosterone is also higher in the morning. At market open, many traders are quite literally at a physiological peak for alertness and aggression — this helps explain the classic opening-bell volatility.

By midday, cortisol dips and testosterone often levels out, encouraging calmer, more analytical decision-making. As the day nears its end, deadlines and the closing bell can nudge cortisol back up, sparking a final hour of anxious position-closing or bold attempts to lock in gains.

Practical Trading Takeaways​

  • Track Your Highs and Lows: Recognize when morning testosterone might make you overconfident or when rising stress might trigger excessive caution.
  • Time Your Critical Decisions: If possible, schedule important analyses or trades when your mind (and hormones) are relatively calm — often mid-morning or midday.
  • Manage "Winner" and "Loser" Effects: A big win can ramp up testosterone and dopamine, making you reckless. A streak of losses elevates cortisol, making you fearful. Take short breaks to reset emotionally.
  • Align with Natural Energy Cycles: The opening bell may be your best window for decisive action if you can harness morning momentum without succumbing to bravado.
  • Healthy Lifestyle, Healthy Hormones: Good sleep, a balanced diet, regular exercise, and stress-management techniques help regulate testosterone, cortisol, dopamine, and serotonin.

Conclusion​

Hormones may be invisible, but they wield real influence over traders' decisions. Testosterone can supercharge confidence and risk-taking, cortisol can push you to fight or flee, dopamine can spark both motivation and recklessness, and serotonin is the unsung hero of rational calm. By recognizing these fluctuating forces, day and swing traders can better avoid emotional extremes. Mastering the markets may also require mastering your internal chemistry.

References​

  1. Coates & Herbert (2008) — Endogenous steroids and financial risk taking on a London trading floor, PNAS — https://www.pnas.org/doi/10.1073/pnas.0704025105
  2. Herbert (2018) — Testosterone, Cortisol and Financial Risk-Taking, Frontiers in Behavioral Neuroscience — https://www.frontiersin.org/articles/10.3389/fnbeh.2018.00101/full
  3. Sapra, S. et al. (2012) — A Combination of Dopamine Genes Predicts Success by Professional Wall Street Traders, PLOS ONE — https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0030844