An analysis of what’s generating the most review articles

BACKGROUND: I was curious why some topics in neuroscience generate more review articles than others. It seems like particularly trendy topics get reviewed every other week. I’ve had a longstanding interest in the crests and troughs of neuroscience’s hotspots. My hypothesis was that research fads would show up as relatively over-reviewed. The corollary to this is that once a trendy topic’s shine wears off, it will revert back to the mean publication : review ratio.

METHODS: I went through PubMed and tallied both the number of total publications over the past 5 years as well as the number of reviews over the same time period. Originally I was entering these by hand, but now I have a matlab script that will handle it. Afterwards, I went through and color-coded the keywords based on their meaning. I picked search terms that interest me. It was not very systematic.

RESULTS: What you see above is a rank-ordered list of all the keywords I could think of while running a particularly mindless behavioral test one Saturday afternoon [if you have suggestions for more / better terms, please let me know]. The review:pub ratio is low when a subject can’t go more than a few articles without needing a new review, and high when the papers pile up in between reviews.

The Over-Reviewed: The subjects with the most reviews relative to other publications supported the trend hypothesis: gut-brain-microbiome and epigenetic stuff. After that came maternal-brain /immune-brain / maternal-immune followed by everyone’s favorite wundermethod: optogenetics.

The Under-Reviewed: Here I saw a grab-bag of methodologies: DTI, transcriptomics, resting-state fMRI and environmental enrichment. Also, the hippocampus, presumably because that vein has been mined to exhaustion.

DISCUSSION: By and large, the hypothesis that trendy topics get reviewed more frequently seems to have been supported. That said, I’m not completely confident I was able to come up with perfectly suitable comparisons. It turns out it’s pretty hard to think up a research area that is new like gut-brain interactions but not ‘trendy’ in that hard-to-define way. I hope this pub:review ratio helps remove some of the subjectivity.

DISCLAIMER: Please let me know if someone has done this sort of thing before and done it better. Also please let me know if you have any suggestions.

Can we take a moment to appreciate that the fields of gut-brain interactions and brain epigenetics can’t even go 2 original articles without someone writing up a review? At that level, what’s the point of an original article’s Discussion section?

SURPRISES: Here are all the things that stuck out to me:

“maternal brain” I did not think this would rank so high, shrug?

“vasopressin” > “oxytocin” I definitely thought that would be the other way around. It turns out when you include ‘brain’ then “oxytocin brain” (3.5) is more reviewed than “vasopressin brain” (4.0). This jives with my stereotype as oxytocin being trendier in the brain than its arginine-substituted cousin.

“adult neurogenesis” was going to be my prototypical subject which used to be trendy but has since lost its appeal, however, I guess the fat lady hasn’t sung quite yet. Also, it was not all that much more reviewed 10 or 15 years ago, in what I would consider its heyday.

What gives “CRISPR”? I thought you were THE trendy, rebellious teeny bopper of the science world?

In general, Broad Research Area > Disease > Specific Brain System > Specific Brain Region > Methodology. There’s a lot of variance in methodology however, with some clear cool kids and some clear losers disclaimer: I do DTI and have dabbled in resting-state fMRI :(

Well, that’s it for now. I’ll keep updating this with more search terms and any refinements I can think of / you suggest. I’m especially interested in areas that used to be hot. In the meantime, let me know if you want to write a review on the change in hippocampal transcriptome following environmental enrichment.