Smart people are less likely to go mad
That's an easy to understand heading, is it not? It's my summary of an article titled: "Association of Heritable Cognitive Ability and Psychopathology With White Matter Properties in Children and Adolescents". It appeared in JAMA Psychiatry. Published online January 24, 2018
By a Norwegian, a German and a Vietnamese (Dag Alnæs, Tobias Kaufmann and Nhat Trung Doan), all of whom work at Oslo University Hospital, Oslo, Norway
Importance: Many mental disorders emerge during adolescence, which may reflect a cost of the potential for brain plasticity offered during this period. Brain dysconnectivity has been proposed as a common factor across diagnostic categories.
Objective: To investigate the hypothesis that brain dysconnectivity is a transdiagnostic phenotype in adolescence with increased susceptibility and symptoms of psychiatric disease.
Design, Setting, and Participants: We investigated clinical symptoms as well as cognitive function in 6487 individuals aged 8 to 21 years from November 1, 2009, to November 30, 2011, in the Philadelphia Neurodevelopmental Cohort and analyzed diffusion magnetic resonance imaging brain scans for 748 of the participants.
Main Outcomes and Measures: Independent component analysis was used to derive dimensional psychopathology scores, and genome-wide complex trait analysis was used to estimate its heritability. Multimodal fusion simultaneously modeled contributions of the diffusion magnetic resonance imaging metrics fractional anisotropy, mean diffusivity, radial diffusivity, L1 (the principal diffusion tensor imaging eigen value), mode of anisotropy, as well as dominant and secondary fiber orientations, and structural connectivity density, and their association with general psychopathology and cognition.
Results: Machine learning with 10-fold cross-validation and permutation testing in 729 individuals (aged 8 to 22 years; mean [SD] age, 15.1 [3.3] years; 343 females [46%]) revealed significant association with general psychopathology levels (r = 0.24, P < .001) and cognition (r = 0.39, P < .001). A brain white matter pattern reflecting frontotemporal connectivity and crossing fibers in the uncinate fasciculus was the most associated feature for both traits. Univariate analysis across a range of clinical domains and cognitive test scores confirmed its transdiagnostic importance. Both the general psychopathology (16%; SE, 0.095; P = .05) and cognitive (18%; SE, 0.09; P = .01) factor were heritable and showed a negative genetic correlation.
Conclusion and relevance: Dimensional and heritable general cognitive and psychopathology factors are associated with specific patterns of white matter properties, suggesting that dysconnectivity is a transdiagnostic brain-based phenotype in individuals with increased susceptibility and symptoms of psychiatric disorders.
Comment: Aren't you glad I summarized that for you? To be fair, they had to tell you all that stuff to make their point. And what they say goes well beyond my simple summary. They found that a particular brain feature was associated with (and probably caused) both low IQ and a variety of mental disorders. And it was all genetically inherited.
So to make it simple again: Some people are born with defective brains. That's not terribly new news, of course. What is interesting is that a particular brain feature, "dysconnectivity", underlies both personality and IQ. You can be both dumb and off your head at the same time!
And that relates well to something I have been saying for a long time: That a high IQ tends to be just one symptom of general biological fitness. "To him that hath, more will be given him", as Jesus said several times (Matthew 13:12 & 25:29; Mark 4:25). There is no equality in nature. We knew that already but it is nice to see it in a particular brain feature.