Inattention Predicts Increased Thickness of Left Occipital Cortex in Men with Attention-Deficit/Hyperactivity Disorder

Abstract

Background: Attention-deficit/hyperactivity disorder (ADHD) in adulthood is a serious and frequent psychiatric disorder with the core symptoms inattention, impulsivity, and hyperactivity. The principal aim of this study was to investigate associations between brain morphology, i.e., cortical thickness and volumes of subcortical gray matter, and individual symptom severity in adult ADHD.

Methods: Surface-based brain morphometry was performed in 35 women and 29 men with ADHD using FreeSurfer. Linear regressions were calculated between cortical thickness and the volumes of subcortical gray matter and the inattention, hyperactivity, and impulsivity subscales of the Conners Adult ADHD Rating Scales (CAARS). Two separate analyses were performed. For the first analysis, age was included as additional regressor. For the second analysis, both age and severity of depression were included as additional regressors. Study participants were recruited between June 2012 and January 2014.

Results: Linear regression identified an area in the left occipital cortex of men, covering parts of the middle occipital sulcus and gyrus, in which the score on the CAARS inattention subscale predicted increased mean cortical thickness [F(1,27) = 26.27, p < 0.001, adjusted R² = 0.4744]. No significant associations were found between cortical thickness and the scores on CAARS subscales in women. No significant associations were found between the volumes of subcortical gray matter and the scores on CAARS subscales, neither in men nor in women. These results remained stable when severity of depression was included as additional regressor, together with age.

Conclusion: Increased cortical thickness in the left occipital cortex may represent a mechanism to compensate for dysfunctional attentional networks in male adult ADHD patients.

Keywords: FreeSurfer; attention; attention-deficit/hyperactivity disorder; cortical thickness; gray matter; morphometry; occipital cortex.

Figure 1

The score on the Conners Adult ADHD Rating Scales inattention subscale predicts cortical thickness in a left occipital area in men, covering parts of the middle occipital gyrus (1) and sulcus (2), but not in women. The uncorrected results of FreeSurfer’s surface-based analysis (p < 0.01) are shown in panel (A) for women and panels (B,C) for men. After cluster-wise correction for multiple comparisons, only the left occipital area in men remains significant [p < 0.01 (E,F)]. No significant associations between cortical thickness and inattention were found in women (D). In panel (G), individual mean cortical thickness in the left occipital area seen in panels (E,F) is shown as a function of the inattention score. Regression line and 95% confidence intervals (gray shade) are displayed [F(1,27) = 26.27, p < 0.001, adjusted R² = 0.4744].

Figure 2

The scores on the Conners Adult ADHD Rating Scales inattention, hyperactivity, and impulsivity subscales are shown as a function of age for all participants (left column), women (middle column), and men (right column). Regression line and 95% confidence intervals (gray shade) are displayed.

Figure 3

Cortical areas in which cortical thickness significantly decreases with age are shown in blue after cluster-wise correction for multiple comparisons (p < 0.01) for all patients (n = 64).