Brain structural correlates of irritability: Findings in a large healthy cohort

Abstract

Irritability and nonviolent aggression are common behavioral features across the population, yet there is limited neurobiological research into subclinical phenotypes representing the lower edge of a symptom continuum ranging from slight irritability to criminal violence. We studied brain structural correlates of irritability in a large healthy cohort to test the hypothesis of associations with fronto-limbic brain structures implicated in mood regulation. In a large multicenter effort, we recruited 409 mentally healthy adults from the community, who received T1-weighted high-resolution 3 T MRI scans. These structural scans were automatically preprocessed for voxel- and surface-based morphometry measurements with the CAT 12 toolbox implemented in SPM 12. Subclinical aggressive symptoms were assessed using the SCL-90-R aggression/hostility subscale and then correlated with cortical volume (VBM), and cortical thickness and gyrification. VBM analysis showed significant (P < 0.05, FDR-corrected at peak-level) positive correlations of cortical volume with SCL-90-R aggression subscale values in large clusters spanning bilateral anterior cingulate and orbitofrontal cortices and left lingual and postcentral gyri. Surface-based morphometry yielded mostly uncorrected positive correlations with cortical thickness in bilateral precentral gyri and with gyrification in left insula and superior temporal gyrus. Our findings imply an association of subclinical aggressive symptoms with cortical volume in areas important for emotion awareness and regulation, which might also be related to cortical adaptation to mental stress. These results overlap with several findings on impulsive aggression in patients suffering from affective and disruptive behavior disorders. They also suggest a biological symptom continuum manifesting in these brain areas. Hum Brain Mapp 38:6230-6238, 2017. © 2017 Wiley Periodicals, Inc.

Keywords: VBM; cortical thickness; gyrification; healthy subjects; subclinical aggression.

Figure 1

Clusters of significant positive correlation of cortical volume with SCL90‐R aggression subscale values (P < 0.05, FDR‐corrected at peak level), shown as (A) maximum intensity projection and (B) slice overlay on an average image calculated from grey‐matter maps of overall participants. [Color figure can be viewed at http://wileyonlinelibrary.com]

Figure 2

Clusters of significant positive correlation of cortical thickness with SCL90‐R aggression subscale values (P < 0.001, uncorrected at peak level). The underlying surface is the average central surface. [Color figure can be viewed at http://wileyonlinelibrary.com]

Figure 3

Clusters of significant positive correlation of cortical gyrification with SCL90‐R aggression subscale values (P < 0.001, uncorrected at peak level). The underlying surface is the inflated average surface. [Color figure can be viewed at http://wileyonlinelibrary.com]