The purpose and finding of this 2017 UK meta-analysis of human epigenetics and cognitive abilities was:
“A meta-analysis of the relationship between blood-based DNA methylation and cognitive function.
We identified [two] methylation sites that are linked to an aspect of executive function and global cognitive ability. The latter finding relied on a relatively crude cognitive test..which is commonly used to identify individuals at risk of dementia.
One of the two CpG sites identified was under modest genetic control..there are relatively modest methylation signatures for cognitive function.”
The review’s stated limitations included:
“It is, of course, possible that a reliable blood-based epigenetic marker of cognitive function may be several degrees of separation away from the biological processes that drive cognitive skills.
There are additional limitations of this study:
- A varying number of participants with cognitive data available for each test;
- Heterogeneity in relation to the ethnicity and geographical location of the participants across cohorts; and
- Relating a blood-based methylation signature to a brain-based outcome.
A 6-year window [between ages 70 and 76] is possibly too narrow to observe substantial changes in the CpG levels.”
All of these limitations were known before the meta-analysis was planned and performed. Other “possible” limitations already known by the 47 coauthors include those from Genetic statistics don’t necessarily predict the effects of an individual’s genes.
The paper referenced studies to justify the efforts, such as one (cited twice) coauthored by the lead author of A problematic study of DNA methylation in frontal cortex development and schizophrenia:
“Epigenome-wide studies of other brain-related outcomes, such as schizophrenia, have identified putative blood-based methylation signatures.”
Was this weak-sauce meta-analysis done just to plump up 47 CVs? Why can’t researchers investigate conditions that could make a difference in their fields?
Was this meta-analysis done mainly because the funding was available? I’ve heard that the primary reason there are papers like the doubly-cited one above is that the US NIMH funds few other types of research outside of their biomarker dogma.
The opportunity costs of this genre of research are staggering. Were there no more productive topics that these 47 scientists could have investigated?
Here are a few more-promising research areas where epigenetic effects can be observed in human behavior and physiology:
- Human studies that follow-up the findings of Chronic pain causes epigenetic changes in the brain and immune system;
- Human intergenerational and transgenerational epigenetic inheritance; and
- Human treatments and therapies that reverse the causes of adverse epigenetic changes.
I hope that the researchers value their professions enough to make a difference with these or other areas of their expertise. And that sponsors won’t thwart researchers’ desires for difference-making science by putting them into endless funding queues.
https://www.nature.com/articles/s41380-017-0008-y “Meta-analysis of epigenome-wide association studies of cognitive abilities”