Lumpers and Splitters in Psychiatry

For most individuals it is hard to understand that psychiatric diagnosis is an issue. We are all so used to going to physicians and finding out if we have a condition, or not, that it is hard to accept that the entire system for psychiatric diagnosis is broken. Unfortunately, this issue impacts many individuals, and the issues date back over 40 years.

The most widely used diagnostic criteria for diagnosis is the Diagnostic and Statistical Manual, DSM. The modern version was introduced in 1980 (DSM-III) to solve a problem with huge variability in diagnosis between physicians. It is a comprehensive guide to assessing and diagnosing mental illness. It has been updated twice since then and is now in its fifth edition from 2013 (DSM-V). While it is based upon research it is fundamentally flawed. Many professionals have made this case.

Lumpers and Splitters

Today’s diagnostic criteria reflects the outcome of different schools of thought about how to approach psychiatric diagnoses, sometimes referred to as “lumpers” and “spitters.” Prior to 1980, the ‘lumper’ approach was used.

Lumpers tend to think of mental illness diagnoses as a spectrum, where individuals are ‘lumped together’ into broad diagnostic criteria (a non-specific anxiety disorder, for example). It is still occasionally seen, for example in Autism Spectrum Disorder, overall, however, the DSM-III and its successors lost out to the ‘splitter’ approach.

Splitters advocate separating diagnoses into multiple different subtypes on the basis that each one is in some way unique. This is seen in the multiple types of anxiety disorder, for example. To achieve this splitters think in terms of categorical yes / no answers when evaluating criteria, and you either have something or you don’t.

In many medical conditions, a splitter approach is very useful–you are either pregnant or you are not. But this doesn’t work in mental health, as it ignores the reality of patient experiences. This approach allows no nuance, no broad acceptance that mental health is not either a yes or a no, and no recognition that psychiatry is full of maybes.

It also ignores the fact that most individuals have ‘mixed’ symptoms and meet criteria for more than one ‘condition’ (so-called ‘comorbid’ conditions). In mental health there are no symptoms which only belong to a single diagnosis (ie are ‘pathognomic’ of a condition). In reality there is a vast overlap of symptoms between various ‘disorders’, which should instead be better conceptualized as part of a larger spectrum.

Impact of Different Diagnostic Perspectives

In my book, The Promise of Psychedelics, I share the story of a man we’ll call Tom. Here’s what we know about Tom:

He’s in his mid-twenties.

· He was abused as a child.

· He was bullied at school.

· He doesn’t have many friends.

Tom is seen in the emergency room, tearful and sad, and considering self-harm (again). He also appears to be inebriated and in the recent past has used multiple drugs including cocaine, cannabis and benzodiazepines. This isn’t the first time he’s shown up like this, and over the past 3 weeks he’s also repeatedly been to his family doctor complaining about anxiety and panic attacks, which have been getting worse. He is having trouble both at work and in his personal life. Anyone who works in this field will know patients like Tom.

Battle of the Diagnostic Perspectives

If I were Tom’s psychiatrist, using a ‘lumper’ perspective, I’d conclude that Tom has symptoms of both depression and an anxiety on a background of trauma, low self-esteem, and self-harming behaviour, and is using self-medication. as a coping mechanism. My assessment would primarily describe Tom’s presenting behaviors without breaking them down into multiple diagnoses.

Contrast this with the splitter perspective used in the DSM-V. Here it is quite possible Tom could meet diagnostic criteria for as many as SEVEN different psychiatric diagnoses, including (1) Major Depressive Disorder, (2) Generalized Anxiety Disorder, (3) Panic Attack Disorder, (4) Post-Traumatic Stress Disorder, (5) Alcohol Use Disorder, (6) Other (or Unknown) Substance Use Disorder, and (7) Borderline Personality Disorder.

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What Next?

There is no holistic research on complex patients such as Tom, as it is only ever focused on a single diagnosis (or very occasionally two). So how do we help such individuals who have such a wide array of diagnoses? Where do we start, and if we don’t understand the patient how can we provide rational treatment for them?

These issues are why mental health diagnosis is broken. It doesn’t reflect either what happens to individuals, or describe the brain changes that may underlie them. The ‘lumper’ or spectrum approach, though spurned for many decades, turns out to be correct. We need to move our diagnostic criteria to this, and design much more personalized treatments using a modular approach. I hope this is incorporated into DSM-VI, but won’t hold my breath.

You can learn more about those risks, as well as the benefits, in my book: The Promise of Psychedelics, Science-Based Hope for Better Mental Health.

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