I Bet You Weren’t Expecting a Post About Ceteris Paribus
…but I like to keep things interesting. I was an economics major in college which means I’m a bit of a nerd, which is why I wrote about ceteris paribus and its parallels in Western medicine.
For those not as familiar, economics is pretty interesting and dynamic: economic philosophy, real-world application, macro and micro theory, statistics, modeling. It’s a nice balance of words and numbers. Some of its theories are broadly applicable and relevant to everyday life which is also cool.
But one concept always troubled me: ceteris paribus. It’s a Latin phrase meaning “all other things being equal.” It’s a tool economists use to isolate cause and effect in order to build manageable theories. For example, holding supply constant, a price increase reduces quantity demanded. Clean. Logical. Easy to understand in theory.
The problem is that’s just not how the real world works. Change one variable and everything else doesn’t just sit still. Everything ripples: general equilibrium effects, feedback loops, emergent behaviors. Markets don’t stay “equal.” They adapt, substitute, and surprise us.
The more I’ve learned about the gap between our Western medicine lens of health and what health actually entails, the more it reminds me of the frustration I had as a 20-year-old econ student trying to make peace with ceteris paribus.
The Reductionist Lens: Medicine’s Ceteris Paribus
Western medicine often operates under an implicit ceteris paribus assumption. Identify the “broken” part—a high biomarker, a single pathway, a specific symptom—then intervene with a targeted fix (a drug, procedure, or surgery), assuming the rest of the body will hold steady.
It’s the medical equivalent of partial-equilibrium analysis: zoom in on one system, fix the number, and move on.
This approach has delivered miracles, especially for acute problems: emergency surgery for trauma, insulin for type 1 diabetes, life-saving interventions in critical care. Reductionism shines when there’s a clear, single-cause culprit.
But for chronic conditions like metabolic syndrome, autoimmune disease, heart disease, mental health struggles, it starts to crack.
The body isn’t a machine with isolated parts. It’s a complex adaptive system, just like an economy. Variables are deeply interconnected through feedback loops, compensatory mechanisms, inflammation cascades, microbiome shifts, gene expression changes, and environmental inputs.
Nothing stays “equal.”
Real-World Ripples: Where Ceteris Paribus Falls Apart
Antibiotics: identify harmful bacteria → eliminate them → problem solved.
But in reality, antibiotics don’t just target a single pathogen—they disrupt an entire microbial ecosystem. The gut microbiome, which plays a critical role in digestion, immune regulation, inflammation, and even neurotransmitter production, gets collateral damage.
This disruption can:
Reduce microbial diversity (a key marker of health)
Allow opportunistic organisms (like Candida or C. diff) to overgrow
Alter short-chain fatty acid production (impacting gut lining integrity and inflammation)
Affect immune signaling and tolerance
Increase long-term susceptibility to infections and antibiotic resistance
There’s also growing evidence linking repeated antibiotic use to downstream issues like metabolic dysfunction, autoimmune conditions, allergies, and even mood disturbances via the gut-brain axis.
It’s not just “kill the bad bacteria.” It’s reshaping an entire internal ecosystem—often with effects that outlast the original infection.
It’s the economic equivalent of intervening in one sector and unintentionally destabilizing multiple others.
SSRIs: increase serotonin in the brain to correct a chemical imbalance, improving mood
What actually happens: serotonin is a whole-body signaling molecule, with the majority produced in the gut, not the brain. SSRIs don’t act in isolation; they influence gut function, microbiome composition, immune signaling, and metabolic pathways.
These broader effects help explain:
Gastrointestinal side effects
Changes in weight and metabolism
Impacts on sleep and sexual function
Variability in treatment response
Emotional blunting or adaptation over time
The delayed therapeutic effect (weeks, not hours) already signals that downstream system-wide changes—not just serotonin levels—are at play.
In practice, many people experience partial relief, side effects, or new symptoms because the drug is interacting with an interconnected system—not a single isolated imbalance.
The Bigger Pattern
Blood pressure medications, painkillers, and most other medical interventions often follow a similar pattern: treat one marker, then manage the side effects that ripple outward, sometimes leading to additional interventions.
Even randomized controlled trials, “the gold standard,” attempt to enforce ceteris paribus through controlled conditions. They’re incredibly useful, but real humans don’t live in controlled environments. Diet, stress, sleep, environment, and genetics don’t stay constant.
External validity suffers, just like economic models that work beautifully on paper but fall apart in the real world.
Why This Matters Now
Chronic disease rates continue to rise despite incredible advances in technology and medicine.
Part of the issue may be that we’re still applying a powerful—but limited—framework to systems that are inherently complex.
Reductionism is excellent at isolating problems. It struggles when the problem is the system itself.
This is where the shift is happening: Systems biology, network medicine, and integrative approaches are the health-world equivalents of complexity economics. They embrace feedback loops, interdependence, and the full web of interactions—rather than pretending “all else” stays equal.
Final Thought
I’ve come to appreciate ceteris paribus as a useful starting point, but a dangerous one if we forget it’s a simplification.
The same goes for health. The body, like the economy, rewards people who zoom out, trace the ripple effects, and work with complexity instead of trying to override it.
