Stress Disorder

Last week, we noted along with many news outlets that a biomarker had been apparently discovered for PTSD. The researchers claimed they had a new tool to help make a differential diagnosis of posttraumatic stress disorder (PTSD).

The tool is a brain scanning technology that, like EEG, measures the brain’s electrical activity. But instead of directly measuring such activity, it measures magnetic fluctuations in the electrical activity. The technique is called MEG. There are certain technical benefits to this method as compared to a traditional EEG, so some researchers are exploring its greater use.

Mind Hacks has a very good analysis of why the researchers’ claims were overreaching and a bit ridiculous:

Crucially, the scan didn’t pick out cases of PTSD among people with a range of mental illnesses, it just found a difference between people with PTSD and healthy people. But this is not a diagnosis, it’s just a difference. […]

The difference could be due to levels of anxiety, common in many mental disorders, or to people who’ve experienced life threatening situations, regardless of whether they have PTSD or not, or any other factor I’ve not accounted for.

Precisely. The study measured only two groups of people — “healthy people” and people the researchers knew had PTSD. What the researchers did not measure is the MEG of a person with depression, or anxiety, or any other mental condition.

Without knowing what each and every other mental conditions’ MEG pattern looks like, this new tool really isn’t very helpful at all. What they believe to be the “PTSD MEG pattern” may very well just be a general pattern for anyone who experiences anxiety. Or nightmares. Or trauma of any sort (whether or not they could actually be diagnosed with PTSD).

The researchers had to have known this simple fact about how differential diagnoses are made (otherwise, why are they using such terms). And yet, incredibly, they still make the claim that their tool and findings can help in making a differential diagnosis:

In this case, the researchers wrongly suggest in their scientific article that their findings “can be used for differential diagnosis” and so we can hardly blame the media for picking up on the hype.

It’s astounding when researchers make patently false claims such as this. And given this was a direct quote from one of the researchers, this is a time where we cannot blame the media for over-simplifying. This is a part of an increasingly disturbing trend of researchers making extraordinary claims that go far beyond their actual data. The most common claim made by researchers nowadays is suggesting there is a causal relationship between two things when their research was designed only to demonstrate a correlation between two things.

It’s an interesting finding — intellectually — but it certainly does not change how PTSD is diagnosed and whether we’ve truly found a “biomarker” for this disorder.

We already had a fairly reliable tool for diagnosing PTSD — it’s called the DSM-IV. And while not ideal, it can more reliably make a differential diagnosis than a MEG can today.

Read the full Mind Hacks critique: Brain scan diagnoses misunderstanding of diagnosis