What Happens to Your Brain During a Market Crash?
8lends5 min read·Just now--
Your brain literally shuts down when you’re standing on the edge of important decisions? Yes, many people all over the world can relate to that, especially when those decisions are related to finances.
March 16, 2020. The Dow Jones plunges 12.9% in a single day — the largest one‑day drop since 1987. The VIX, the market’s fear index, soars to 82.69, its highest level since the 2008 financial crisis.
Thousands of investors open their brokerage apps and hit “sell.” It seemed like the right decision back then. But no one really made such a decision based on logic. People were unable to think rationally and sold their assets on emotion.
But why didn’t people stop and think about the whole situation before selling?
When you see several huge red candles in a row, and a value drops 10%, your brain doesn’t register it as food for thought — it registers it as a threat.
The amygdala, the brain’s rapid threat‑detection system, evolved to respond to immediate physical dangers, like a predator. However, financial losses can activate the same fear circuitry because the amygdala learns to treat any potential harm (including a dropping portfolio) as a threat.
It doesn’t distinguish between a bear and a bear market, but its core function — triggering a “danger” signal — can be engaged by both. This signal initiates a biochemical cascade: adrenaline and cortisol are released, sharpening some senses while impairing complex reasoning.
Contrary to the popular “blood shunting” myth, the prefrontal cortex does not shut down; rather, stress hormones modulate its activity, biasing it toward habitual, emotional responses and away from deliberate, analytical thought. This is not a primitive override but a shift in cognitive priorities — one that can make selling during a crash feel as urgent as running from a predator, even though the situations are objectively different.
It’s ironic how a part of our brain that used to save our ancestors from threats now makes people lose millions of dollars.
How trading destroys your decision-making abilities
Neuroeconomic studies have documented that investors experiencing acute financial stress show a 40‑60% decrease in activity in the areas of the brain responsible for complex decision‑making. At the same time, activity in the primitive emotional centers increases by 30‑50%.
When you see a price moving closer to the liquidation level, your brain loses approximately half its analytical capacity, and your emotional response is heightened by 50%. You make decisions with your rational part turned off, and your emotional part turned up to full.
Cambridge professor John Coates measured cortisol in active traders and found that elevated levels of the stress hormone suppress the prefrontal cortex while simultaneously increasing the reactivity of the amygdala. Red candles and bearish posts on X don’t just disturb your peace — they steadily raise your cortisol. The more you stare at the chart, the worse your judgment gets.
Elephant and Rider
Psychologist Jonathan Haidt described the architecture of human decision‑making through an image that’s hard to forget.
Two competing centers of the investor’s psyche: an emotional elephant and its rational rider. The rational part of the mind likes to think it controls emotions. In calm circumstances, it does. But when things go south, emotions take control — the elephant rebels against the rider, and in this confrontation, the elephant’s primitive strength wins every time.
The Price of One Decision Under Cortisol
March 2020. The S&P 500 loses 34% in 23 trading days. Many are selling. On March 16, 2020, the Dow fell nearly 3,000 points — almost 13% — to 20,188. Many investors exited and missed the recovery. By December 31, 2020, the Dow had risen to 30,606 — about 51% higher than that March close.
A single, cortisol‑fueled decision cost these people half their recovery.
J.P. Morgan Chase research shows that 10,000 invested in the S&P 500 at the beginning of 2000 and left there would have been worth 32,421 by the end of 2019. But if you miss the 10 best trading days, you’ll be worth less than half: $16,180.
The problem is that most of the best days happen right after the worst ones. You all know this feeling well: when you enter a long position, the price drops; when you enter a short position, the price spikes. Sounds familiar, right?
The Four Stages of Neurobiological Entrapment
Stage 1. Trigger.
You see a red screen. Your amygdala activates a threat response before you’ve consciously processed what’s happening — within a fraction of a second.
Stage 2. Hormonal cascade.
Adrenaline surges immediately; cortisol builds over minutes, not seconds. The prefrontal cortex doesn’t shut down, but its function is impaired — the amygdala bombards it with distress signals, making deliberate, long‑term thinking harder.
Stage 3. Tunnel thinking.
You lose the five‑year plan. Stress narrows attention to the immediate threat. Evolutionarily useful for a predator, but disastrous for a portfolio, where inaction is often the winning move.
Stage 4. Action.
You sell, or cash out. Doing something feels like regaining control, and it reduces anxiety faster than doing nothing. But research shows the urge to act doesn’t always mean the decision is rational. Sometimes the most powerful thing you can do is nothing at all.
Why The Same Experience Doesn’t Protect
It sounds right to assume that someone who lived through the 2008 crash wouldn’t panic in 2020. After all, they know the market recovers. Neuroscience suggests otherwise.
Repeated exposure to market crashes can rewire the brain to be more sensitive to losses, creating a feedback loop of increased risk aversion and fear‑based decisions, even in relatively stable conditions.
In other words, the more crashes you’ve seen, the faster your stress response kicks in. Experience doesn’t make you calm.
This explains why experienced investors sometimes panic more than novices. They have more “cortisol memory.”
How to Stop Losing Money
Knowledge of the mechanism is not protection. You can’t “decide” not to be afraid. But you can build a system that makes decisions for you when you’re biologically incapable of doing so rationally.
First, set the rules before the crash. Stop‑loss orders, holding periods, and acceptable drawdown percentages — all of this should be determined in a calm state, when the prefrontal cortex is working at full capacity.
Second, turn off the screen. A short walk can reset the brain and reduce cortisol levels.
Third, choose instruments whose mechanics aren’t dependent on daily revaluations. If your income is determined not by the price of an asset on the screen, but by a specific contract with a specific borrower, you have fewer physical reasons to open a brokerage app in a panic.
This is precisely the logic behind the model 8lends is building. The yield on a P2P loan doesn’t change if the index falls by 10%. The borrower pays the interest under the contract, regardless of what happens to the VIX. This isn’t immunity from all risks, but it’s protection against the most costly of all: your own brain in a moment of panic.
The elephant still wins sometimes. But if the rider has rules written down in advance, the odds are evened out.
Sources:
1. Tactical Investor — Investment Fear and Neuroeconomics (2025);
2. Hartford Funds — The Cortisol Effect;
3. Heritage Investment Group — Your Brain During a Stock Market Crisis;
4. Campaign for a Million — John Coates cortisol research;
5. CGAA — 2020 Stock Market Crash;
6. Money Talks News — JP Morgan Chase 10 best days study;
7. PMC — COVID-19 and investor behavior.
