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The Evidence of the Anecdote

June 8, 2012

The foundation of medical decision-making is “evidence-based medicine.”  As most readers know, this is the effort to use the best available evidence (using the scientific method) to make decisions and recommendations about how to treat individual patients.  “Evidence” is typically rated on four levels (1 to 4).  Level 1 represents high-quality evidence—usually the results of randomized clinical trials—while level 4 typically consists of case studies, uncontrolled observations, and anecdotal reports.

Clinical guidelines and drug approvals typically rely more heavily (or even exclusively) on level-1 evidence.  It is thought to be more valid, more authoritative, and less affected by variations among individuals.  For example, knowing that an antidepressant works (i.e., it gives a “statistically significant effect” vs placebo) in a large, controlled trial is more convincing to the average prescriber than knowing that it worked for a single depressed guy in Peoria.

But is it, really?  Not always (especially if you’re the one treating that depressed guy in Peoria).  Clinical trials can be misleading, even if their results are “significant.”  As most readers know, some investigators, after analyzing data from large industry-funded clinical trials, have concluded that antidepressants may not be effective at all—a story that has received extensive media coverage.  But lots of individuals insist that they do work, based on personal experience.  One such depression sufferer—who benefited greatly from antidepressants—wrote a recent post on the Atlantic Online, and quoted Peter Kramer: “to give the impression that [antidepressants] are placebos is to cause needless suffering” because many people do benefit from them.  Jonathan Leo, on the other hand, argues that this is a patently anti-scientific stance.  In a post this week on the website Mad In America, Leo points out (correctly) that there are people out there who will give recommendations and anecdotes in support of just about anything.  That doesn’t mean they work.

Both sides make some very good points.  We just need to find a way to reconcile them—i.e., to make the “science” more reflective of real-world cases, and use the wisdom of individual cases to influence our practice in a more scientifically valid way.  This is much easier said than done.

While psychiatrists often refer to the “art” of psychopharmacology, make no mistake:  they (we) take great pride in the fact that it’s supposedly grounded in hard science.  Drug doses, mechanisms, metabolites, serum levels, binding coefficients, polymorphisms, biomarkers, quantitative outcome measures—these are the calling cards of scientific investigation.  But when medications don’t work as planned (which is often), we improvise, and when we do, we quickly enter the world of personal experience and anecdote.  In fact, in the absence of objective disease markers (which we may never find, frankly), psychiatric treatment is built almost exclusively on anecdotes.  When a patient says a drug “worked” in some way that the data don’t support, or they experience a side effect that’s not listed in the PDR, that becomes the truth, and it happens far more frequently than we like to admit.

It’s even more apparent in psychotherapy.  When a therapist asks a question like “What went through your mind when that woman rejected you?” the number of possible responses is infinite, unlike a serum lithium level or a blood pressure.  A good therapist follows the patient’s story and individualizes treatment based on the individual case (and only loosely on some theory or therapeutic modality).  The “proof” is the outcome with that particular patient.  Sure, the “N” is only 1, but it’s the only one that counts.

Is there any way to make the science look more like the anecdotal evidence we actually see in practice?  I think not.  Most of us don’t even stop to think about how UN-convincing the “evidence” truly is.  In his book Pharmageddon, David Healy describes the example of the parachute:  no one needs to do a randomized, controlled trial to show that a parachute works.  It just does.   By comparison, to show that antidepressants “work,” drug companies must perform large, expensive trials (and often multiple trials at that) and even then, prove their results through statistical measures or clever trial designs.  Given this complexity, it’s a wonder that we believe clinical trials at all.

On the other side of the coin, there’s really no way to subject the anecdotal report, or case study, to the scientific method.  By definition, including more patients and controls (i.e., increasing the “N”) automatically introduces heterogeneity.  Whatever factor(s) led a particular patient to respond to Paxil “overnight” or to develop a harsh cough on Abilify are probably unique to that individual.

But maybe we can start looking at anecdotes through a scientific lens.  When we observe a particular response or effect, we ought to look not just at the most obvious cause (e.g., a new medication) but at the context in which it occurred, and entertain any and all alternative hypotheses.  Similarly, when planning treatment, we need to think not just about FDA-approved drugs, but also patient expectations, treatment setting, home environment, costs, other comorbidities, the availability of alternative therapies, and other data points or “independent variables.”  To use a crude but common analogy, it is indeed true that every person becomes his or her own laboratory, and should be viewed as such.

The more we look at patients this way, the further we get from clinical trials and the less relevant clinical trials become.  This is unfortunate, because—for better or for worse (I would vote for “worse”)—clinical trials have become the cornerstone of evidence-based psychiatry.  But a re-emphasis on anecdotes and individual cases is important.  Because in the end, it’s the individual who counts.  The individual resembles an N of 1 much more closely than he or she resembles an N of 200, and that’s probably the most important evidence we need to keep in mind.

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How To Think Like A Psychiatrist

March 4, 2012

The cornerstone of any medical intervention is a sound diagnosis.  Accurate diagnosis guides the proper treatment, while an incorrect diagnosis might subject a patient to unnecessary procedures or excessive pharmacotherapy, and it may further obscure the patient’s true underlying condition.  This is true for all medical specialties—including psychiatry.  It behooves us, then, to examine the practice of clinical decision-making, how we do it, and where we might go wrong, particularly in the area of psychiatric diagnosis.

According to Pat Croskerry, a physician at Dalhousie University in Canada, the foundation of clinical cognition the “dual process model,” first described by the Greek philosophers (and reviewed here).  This model proposes that people solve problems using one of two “processes”:  Type 1 processes involve intuition and are largely automatic, fast, and unconscious (e.g., recognizing a friend’s face).  Type 2 processes are more deliberate, analytical, and systematic (e.g., planning the best route for an upcoming trip).  Doctors use both types when making a diagnosis, but the relative emphasis varies with the setting.  In the ED, quick action based on pattern recognition (i.e., Type 1 process) is crucial.  Sometimes, however, it may be wrong, particularly if other conditions aren’t evaluated and ruled out (i.e., Type 2 process).  For instance, a patient with flank pain, nausea, vomiting, and hematuria demonstrates the “pattern” of a kidney stone (common), but may in fact have a dissecting aortic aneurysm (uncommon).

This model is valuable for understanding how we arrive at psychiatric diagnoses (the above figure is from a 2009 article by Croskerry).  When evaluating a patient for the first time, a psychiatrist often looks at “the big picture”:  Does this person appear to have a mood disorder, psychosis, anxiety, a personality disorder?  Have I seen this type of patient before?  What’s my general impression of this person?  In other words, the assessment relies heavily on Type 1 processes, using heuristics and “Gestalt” impressions.  But Type 2 processes are also important.  We must inquire about specific symptoms, treatment history, social background; we might order tests or review old records, which may change our initial perception.

Sound clinical decision-making, therefore, requires both processes.  Unfortunately, these are highly prone to error.  In fact, Croskerry identifies at least 40 cognitive biases, which occur when the processes are not adapted for the specific task at hand.  For instance, we tend to use Type 1 processes more frequently than we should.  Many psychiatrists, particularly those seeing a large volume of patients for short periods of time, often see patterns earlier than is warranted, and rush to diagnoses without fully considering all possibilities.  In other words, they fall victim to what psychologist Keith Stanovich calls “dysrationalia,” or the inability to think or act rationally despite adequate intelligence.  In the dual process model, dysrationalia can “override” Type 2 processes (“I don’t need to do a complete social history, I just know this patient has major depression”), leading to diagnostic failure.

Croskerry calls this the “cognitive miser” function: we rely on processes that consume fewer cognitive resources because we’re cognitively lazy.  The alternative would be to switch to a Type 2 process—a more detailed evaluation, using deductive, analytic reasoning.  But this takes great effort and time.  Moreover, when a psychiatrist switches to a “Type 2” mode, he or she asks questions are nonspecific in nature (largely owing to the unreliability of some DSM-IV diagnoses), or questions that confirm the initial “Type 1” hunch.  In other words, we end up finding we expect to find.

The contrast between Type 1 and Type 2 processes is most apparent when we observe people operating at either end of the spectrum.  Some psychiatrists see patterns in every patient (e.g., “I could tell he was bipolar as soon as he walked into my office”—a classic error called the representativeness heuristic), even though they rarely ask about specific symptoms, let alone test alternate hypotheses.  On the other hand, medical students and young clinicians often work exclusively in Type 2; they ask very thorough questions, covering every conceivable alternative, and every symptom in the DSM-IV (even irrelevant ones).  As a result, they get frustrated when they can’t determine a precise diagnosis or, alternately, they come up with a diagnosis that might “fit” the data but completely miss the mark regarding the underlying essence of the patient’s suffering.

Croskerry writes that the most accurate clinical decision-making occurs when a physician can switch between Type 1 and Type 2 processes  as needed, a process called metacognition.  Metacognition requires a certain degree of humility, a willingness to re-examine one’s decisions in light of new information.  It also demands that the doctor be able to recognize when he or she is not performing well and to be willing to self-monitor and self-criticize.  To do this, Croskerry recommends that we develop “cognitive forcing strategies,” deliberate interventions that force us to think more consciously and deliberately about the problem at hand.  This may help us to be more accurate in our assessments:  in other words, to see both the trees for the forest, and the forest for the trees.

This could be a hard sell.  Doctors can be a stubborn bunch.  Clinicians who insist on practicing Type 2,  “checklist”-style medicine (e.g., in a clinical trial) may be unwilling to consider the larger context in which specific symptoms arise, or they may not have sufficient understanding of that context to see how it might impact a patient.  On the other hand, clinicians who rush to judgment based on first impressions (a Type 1 process) may be annoyed by any suggestion that they should slow down and be more thorough or methodical.  Not to mention the fact that being more thorough takes more time. And as we all know, time is money.

I believe that all psychiatrists should heed the dual-process model and ask how it influences their practice.  Are you too quick to label and diagnose, owing to your “dysrational” (Type 1) impulses?  On the other hand, if you use established diagnostic criteria (Type 2), are you measuring anything useful?  Should you use a cognitive forcing strategy to avoid over-reliance on one type of decision-making?  If you continue to rely on pattern recognition (Type 1 process), then what other data (Type 2) should you collect?  Treatment history?  A questionnaire?  Biomarkers?  A comprehensive assessment of social context?  And ultimately, how do you use this information to diagnose a “disorder” in a given individual?

These are just a few questions that the dual process model raises.  There are no easy answers, but anything that challenges us to be better physicians and avoid clinical errors, in my opinion, is well worth our time, attention, and thought.


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