Hickam’s Dictum and the Reality of Multiple Diagnoses

Hickam’s dictum is a medical aphorism usually stated as “a patient can have as many diseases as he damn well pleases.” It serves as a counterweight to the more famous Occam’s razor, which pushes clinicians to find a single diagnosis that explains all of a patient’s symptoms. The dictum is a reminder that real human bodies do not always cooperate with elegant diagnostic logic, and that sometimes the correct answer is not one disease but two or three happening at once. The tension between these two principles shapes how doctors think through difficult cases every day, and misapplying either one can lead to missed diagnoses or unnecessary testing.

Where the Phrase Comes From

The dictum is attributed to John Hickam, an American internist and pulmonologist who taught at Duke University and Indiana University in the mid-twentieth century. As with many medical aphorisms, the exact moment of coining is murky. There is no landmark paper or published lecture where Hickam formally introduced the idea. Instead, the phrase seems to have spread orally through generations of medical trainees who heard it during clinical rounds. The somewhat profane phrasing is part of its staying power. In a profession built on Latin terminology and precise language, the bluntness of “as many diseases as he damn well pleases” makes the point memorable in a way that a politely worded version never would.

What Hickam was pushing back against was a real tendency in clinical reasoning. When a patient walks in with fatigue, joint pain, and a rash, the instinct trained into medical students is to search for one unifying explanation. That instinct is powerful and often correct. But Hickam’s point was that it can become a trap. Sometimes the fatigue is from anemia, the joint pain is from osteoarthritis, and the rash is from an unrelated drug reaction. Three problems, three causes, no elegant unifying thread.

Occam’s Razor in Medicine and Why It Falls Short

Occam’s razor, the principle of parsimony, tells you to prefer the simplest explanation that accounts for all the facts. In medicine, this translates to seeking a single diagnosis that explains a patient’s full set of symptoms. The approach is genuinely useful. It prevents doctors from chasing red herrings, keeps workups focused, and works well in younger patients who tend to present with one acute problem at a time. One analysis frames it this way: all things being equal, one diagnosis rather than several should be sought to explain a patient’s presentation, though the authors note it can also obscure the full picture.¹

The trouble is that “all things being equal” is doing enormous work in that sentence. In practice, things are rarely equal. A seventy-year-old with high blood pressure, diabetes, chronic lung disease, and creaky knees does not have one underlying condition that explains all four problems. Each one has its own cause, its own trajectory, and its own treatment. Trying to force these into a single diagnosis is not parsimonious. It is wrong. Hickam’s dictum exists precisely to flag the situations where the elegant single-diagnosis model breaks down.

How Common Multiple Diagnoses Actually Are

The strongest argument for taking Hickam’s dictum seriously is not philosophical but statistical. Multimorbidity, meaning the coexistence of two or more chronic conditions in one person, is not the exception. It is the norm for a huge share of the population. An analysis of nearly 31 million Medicare beneficiaries found that about two-thirds had multimorbidity. The rate climbed steeply with age: roughly half of those under 65 had two or more chronic conditions, rising to about 62 percent for people aged 65 to 74 and over 80 percent for those 85 and older.²

Those numbers should shift how you think about diagnostic reasoning. If a doctor sees a 78-year-old patient and assumes all their symptoms stem from a single underlying cause, the statistical base rate is working against that assumption. The patient probably has several chronic conditions already, and a new symptom is more likely to reflect a new problem layered on top of existing ones than to represent some grand unifying diagnosis. This does not mean doctors should stop looking for connections between symptoms. It means the threshold for accepting that a patient has multiple independent problems should be much lower than many clinicians were taught.

What “Multiple Diagnoses” Actually Look Like in Practice

A 2024 study took an interesting approach to this question. Researchers examined 83 published case reports that explicitly claimed to demonstrate Hickam’s dictum or violate Occam’s razor. Every case had a primary diagnosis explaining the presenting illness, plus one or more additional diagnoses. The researchers classified those extra diagnoses into four categories, and the results were revealing.³

The most common additional finding, at about 40 percent, was a disease causally linked to the primary diagnosis. In other words, what looked like two separate problems was actually one problem causing another. Roughly 31 percent were pre-existing conditions the patient already had before coming in. About 25 percent were incidentalomas, meaning findings discovered by accident during imaging or testing that were unrelated to why the patient sought care. Only about 4 percent of cases involved a truly independent second disease contributing to the acute presentation.

This is a striking finding and it complicates the simple framing of Occam versus Hickam. The vast majority of cases that get labeled as Hickam’s dictum in action are not really examples of purely independent diseases stacking up by coincidence. They are cases where one disease led to another, where a known condition was already present, or where modern imaging happened to spot something unrelated. Genuine coincidence, two unrelated diseases both actively causing a patient’s current symptoms, turned out to be rare even in a collection of cases specifically selected to illustrate it.

Geriatrics and the Hickam Default

If there is one branch of medicine where Hickam’s dictum is not a corrective but rather the starting assumption, it is geriatrics. Geriatricians are trained to expect multiple simultaneous conditions in their patients. When an older person presents with several different symptoms, the reflexive search for a single unifying diagnosis that dominates internal medicine training gives way to a broader assessment. Hypertension, heart failure, atrial fibrillation, diabetes, osteoarthritis, chronic lung disease, osteoporosis, dementia, and depression are among the most frequently coexisting conditions in elderly patients.⁴

This shift in default thinking has real consequences for treatment. When a patient has six or seven conditions, each with its own guideline-recommended medication, the total pill burden and the risk of drug interactions become problems in themselves. Geriatric medicine has developed its own frameworks for deciding which conditions to treat aggressively and which to manage conservatively, based on what matters most to the individual patient’s quality of life. Hickam’s dictum, in this context, is not just a diagnostic principle. It shapes the entire treatment philosophy.

Saint’s Triad and Other Named Multimorbidity Patterns

Some combinations of independent conditions show up together often enough to have earned their own names. The best-known example is Saint’s triad: the coexistence of gallstones, hiatal hernia, and colonic diverticulosis. These three conditions share risk factors (age, obesity, dietary patterns) but do not cause one another in any direct way. Case reports have documented this combination and discussed clinical similarities, with some authors broadening the triad to include any type of hernia rather than strictly hiatal hernia, based on the theory that a developmental feature of connective tissue might predispose people to multiple hernia types.⁵

Saint’s triad is useful as a teaching tool because it illustrates a point Hickam’s dictum makes abstractly. When a patient with gallstones also has a hiatal hernia and diverticulosis, a doctor who insists on finding a single unifying diagnosis will waste time and possibly subject the patient to unnecessary testing. The correct diagnosis is simply: this patient has three common conditions that happen to coexist, and each one needs to be evaluated on its own merits. Named triads and clusters like this one give clinicians permission to accept multiplicity without feeling like they are being diagnostically lazy.

The Risks of Taking Either Principle Too Far

Both Occam’s razor and Hickam’s dictum can be misapplied, and the consequences look different in each direction. Over-applying Occam’s razor means a doctor keeps searching for a unifying diagnosis when the patient actually has two or more independent problems. This leads to diagnostic delay, repeated testing, growing frustration for the patient, and sometimes real harm. If someone has both celiac disease and a thyroid disorder, insisting that one of them must explain all the symptoms means the other goes untreated.

Over-applying Hickam’s dictum carries its own hazards. If a clinician too readily accepts that a patient has multiple unrelated problems, they may stop looking for the underlying connection that actually exists. They may also order excessive tests, each of which carries a small but real risk of false positives. Those false positives generate more tests, more procedures, and more anxiety in a self-reinforcing spiral sometimes called the cascade effect. The risk of this cascade has been documented: subjecting patients to unnecessary testing carries its own set of risks, as false-positive results get pursued and produce a chain of events that tends to proceed with increasing momentum, becoming harder to stop the further it goes.⁶

The incidentaloma problem is a perfect illustration. Modern imaging is so detailed that CT scans, MRIs, and ultrasounds routinely pick up abnormalities that have nothing to do with why the scan was ordered. A kidney scan turns up a small adrenal nodule. A chest CT reveals a tiny thyroid mass. These findings are almost always benign, but once they are in the medical record, someone has to decide whether to follow up. The physician who embraces Hickam’s dictum too enthusiastically might treat each incidentaloma as a new problem requiring its own workup, when the wisest course is often watchful waiting or simply noting the finding and moving on.

Cognitive Load and the Pressure to Simplify

There is a less discussed reason why the Occam-versus-Hickam tension matters: the conditions under which doctors actually make decisions. Emergency departments, busy clinics, and overnight shifts impose significant cognitive load on physicians, and that load changes how they think. Research has shown that when physicians face higher cognitive demands, they order more diagnostic tests overall but shift toward common, broad-spectrum tests rather than targeted ones. They also show more uncertainty in their diagnostic thinking. Doctors in the highest cognitive load conditions increased hospital admissions by about 28 percent compared to the same physicians working under the lowest load, for identical types of patients.⁷

This has direct implications for how Hickam’s dictum gets applied in real life. A cognitively overloaded doctor may default to Occam’s razor not because the evidence supports it but because holding multiple diagnostic hypotheses in mind simultaneously is harder than pursuing one thread. Alternatively, a fatigued physician might over-accept multiple diagnoses simply because they do not have the bandwidth to search for the connecting thread. Neither failure is about the doctor being incompetent. Both reflect the reality that diagnostic reasoning is shaped by the environment in which it happens, not just by the principles taught in medical school.

When Patients Feel the Consequences

The debate between parsimony and multiplicity is not just an abstract problem for clinicians. Patients live with its consequences. People with genuinely multiple conditions often describe a frustrating pattern: they report a constellation of symptoms, and doctors keep trying to fit everything under one roof. When no single diagnosis works, the patient gets told their symptoms are unexplained, psychosomatic, or exaggerated. Research into the emotional impact of diagnostic delays has found that nearly all patients in one study reported feeling dismissed or not taken seriously by medical professionals, leading to frustration, anger, and self-doubt. When a diagnosis finally arrived, it brought relief and validation, but many patients were left with long-term mistrust in the healthcare system and reluctance to seek future care.⁸

Hickam’s dictum, in this light, is not just a clinical reasoning tool. It is a form of patient respect. Taking seriously the possibility that a person’s varied symptoms might reflect more than one condition means taking that person’s experience seriously. The patient who says “my knee hurts, my stomach is off, and I’m always tired” may not be a diagnostic puzzle with one answer. They may be a person with arthritis, gastritis, and anemia who needs three treatments, not one more round of testing to find the grand unifying theory.

Machine Learning and Multi-Label Diagnosis

The rise of artificial intelligence in healthcare has given the Hickam-versus-Occam question a new dimension. Traditional diagnostic algorithms were designed around the Occam model: input symptoms, output one diagnosis. But machine learning systems are increasingly being built to handle multi-label classification, meaning they can assign more than one diagnosis to a single patient simultaneously. In one study focused on diabetic complications, multi-label classification models outperformed traditional single-label approaches across most performance measures, achieving better accuracy in identifying which patients had multiple complications occurring together.⁹

Separate work has explored using machine learning for general practice triage, where the goal is to route patients to the right department based on limited initial information. This is a setting where the Hickam problem is acute: a patient might need to see both a cardiologist and an endocrinologist, and a system that forces a single departmental label will get it wrong for multimorbid patients.¹⁰

These tools are still in relatively early stages of clinical deployment, and they bring their own risks. An algorithm that too eagerly assigns multiple diagnoses could drive the same overtesting cascade that human physicians face when they overuse Hickam’s dictum. But the technical ability to think in terms of multiple simultaneous conditions rather than a single best guess represents a genuine shift in how diagnostic support systems are being designed. The question is no longer whether to think in Occam’s terms or Hickam’s terms, but how to teach a machine to know when each applies.

How Clinicians Actually Navigate the Tension

In practice, experienced doctors do not rigidly apply either principle. They use Occam’s razor as a starting heuristic and shift toward Hickam’s dictum when the clinical picture resists unification. Certain red flags signal that it is time to stop looking for a single diagnosis: when the patient is elderly and already has known chronic conditions, when symptoms map cleanly onto two well-characterized diseases that share no known causal link, when a prolonged search for a unifying explanation has come up empty, or when the patient’s own narrative suggests distinct problems with distinct timelines.

Dermatology offers one example of a specialty where this toggle happens frequently. Skin findings can be manifestations of systemic disease, which rewards Occam-style thinking. But they can also be entirely independent conditions sitting next to each other on the same patient’s body, making Hickam the better guide. A patient with both psoriasis and a basal cell carcinoma does not have one disease. They have two, and treating one will do nothing for the other.

The deeper lesson of Hickam’s dictum is not really about how many diagnoses a patient has. It is about intellectual humility. The desire for a single clean explanation is human and understandable, but the body is not obligated to be tidy. Accepting that messiness, without either giving up on finding connections or insisting on connections that are not there, is one of the harder skills in clinical medicine. Hickam’s phrasing captures the point with characteristic irreverence: the patient does not care about your diagnostic elegance. They just want you to figure out what is actually wrong.