Tuesday, November 1, 2016

If depression is biological, does that change how you feel about it?

Last week a story reached my twitter feed that I couldn't resist looking into because the claim in the title looked outrageous.

"Depression isn't a choice, it's a kind of brain damage" on Lifehack.org exists under the same title at themindsjournal.com.

In his bio there, the author describes himself as

an introverted extrovert with a thirst for life. He is a full time web developer and freelance programmer. You can find him online at YourFriendlyWebGuy.com. In his spare time he DJs, loves coffee and practices yoga.

Apparently he's also a writer... with the same story all over the place on the net. Is it any good?

The first claim is that researchers have definitively shown (finally) that persistent depression causes brain damage, not the other way round.

That's not where I thought this was going. If the claim in the title is correct - that depression is a kind of brain damage, wouldn't you expect researchers to have shown that brain damage causes depression? So I'm already confused after two sentences - what does Erichsen mean by brain damage, and what by depression?

The next two paragraphs take us down a difficult path:

The study, which consisted of 9,000 individual samples, collected from the ENIGMA group, succeeded in definitively proving a causal relationship between persistent depression and brain damage. Magentic resonance images (MRIs) showed evidence of hippocampus shrinkage in 1,728 patients diagnosed with chronic depression compared to the 7,199 healthy individuals partaking in the study.

Specifically, the study found that those patients diagnosed with major depressive disorder, “showed robust reductions in hippocampal volume (1.24%) in MDD patients compared with healthy controls.” You can read the full study here.

Problems in these paragraphs and beyond:
1. It's unlikely that it definitively proved a causal relationship, because science doesn't often do that, but we'll see...
2. Magentic? Not the most persuasive spelling...
3. 1728 + 7199= 8927. Close to 9000 but not the same. Just sayin'. Notice the big difference in sample size between healthy and chronically depressed. We'll see if that matters.
4. I'll forgive the awkwardness of that quote and skip to the problem of the 'here' bit. There's no link. Eventually I found a facebook post by someone else linking to the story and the original article so we can check some of the claims.
5. The diagram is a little unconventional. Is the hippocampus labelled correctly? Compare... Would we say the amygdala is inside it?
6. Most of my concerns are explained by this article - Erichsen's post is mostly a rewrite that introduces inaccuracies.

The original study (Schmaal et al., 2016) is a meta-analysis of other studies. As such it cannot provide definitive proof but it can do what is otherwise difficult: accumulate a sample size big enough to draw some conclusions about brain changes in people with major depression. There are enormous difficulties in bringing together data from different studies with variables like these: criteria for 'depression' vary and there will be differences in samples and techniques used to carry out scans. Their findings included decreased volume in the hippocampus that was more pronounced among those with earlier onset depression but not among those with more severe symptoms. The researchers speculate that their findings may relate to a premorbid vulnerability factor (abnormal hippocampal development) but there is no way to draw conclusions about this from their data.

So let's be absolutely clear: the study associates the size of brain regions with presence of a diagnosis of major depression. As a cross-sectional study, it does not show that size differences represent atrophy, although this seems a likely cause, and it certainly cannot show that depression causes atrophy or that atrophy causes depression.

So why the title in Erichsen's article? Depression is not a choice - that's fine - I'm not sure who says it is. But the validity of that claim does not rest on proof that depression is causing or caused by changes in the size of brain regions. Erichsen's work misrepresents the original article, borrows heavily from someone else's work online, and then goes on to suggest that the choices you make as a depressed person can cure your depression. The epistemological confusion here as well as misinformation is really unhelpful - yet another example of a desperate attempt to find biological evidence for the mechanisms of depression. Of course they can be found and research like the original here is part of an ever-increasing body of literature that finds correlates of depression in the brain.

But what's the point of writing like Erichsen's that trumpets an unsupportable claim that something has been definitively proven? Why is it so important to identify these biological changes? Is it important to you? How does it change your feelings about depression
a) if biological mechanisms are found, and
b) if you see writing like Erichsen's that is factually inaccurate?

Let us know...

This post written by Alan Law

ResearchBlogging.org Schmaal L, Veltman DJ, van Erp TG, Sämann PG, Frodl T, Jahanshad N, Loehrer E, Tiemeier H, Hofman A, Niessen WJ, Vernooij MW, Ikram MA, Wittfeld K, Grabe HJ, Block A, Hegenscheid K, Völzke H, Hoehn D, Czisch M, Lagopoulos J, Hatton SN, Hickie IB, Goya-Maldonado R, Krämer B, Gruber O, Couvy-Duchesne B, Rentería ME, Strike LT, Mills NT, de Zubicaray GI, McMahon KL, Medland SE, Martin NG, Gillespie NA, Wright MJ, Hall GB, MacQueen GM, Frey EM, Carballedo A, van Velzen LS, van Tol MJ, van der Wee NJ, Veer IM, Walter H, Schnell K, Schramm E, Normann C, Schoepf D, Konrad C, Zurowski B, Nickson T, McIntosh AM, Papmeyer M, Whalley HC, Sussmann JE, Godlewska BR, Cowen PJ, Fischer FH, Rose M, Penninx BW, Thompson PM, & Hibar DP (2016). Subcortical brain alterations in major depressive disorder: findings from the ENIGMA Major Depressive Disorder working group. Molecular psychiatry, 21 (6), 806-12 PMID: 26122586

No comments:

Post a Comment