Gray Matter Volume Alterations Found in Adults With ADHD and Bipolar Disorder

Altered grey matter volume (GMV) in the frontal-striatal and frontal-parietal circuits is evident in adult patients with attention-deficit/hyperactivity disorder (ADHD) and altered GMV in the prefrontal-amygdala circuit exists in adult patients with bipolar disorder type I (BD-I), according to study findings published in Journal of Psychiatric Research.

Researchers conducted a review and meta-analysis of 4580 potential records from EMBASE, PubMed, Web of Science, and PsycINFO databases from January 2018 to September 2021. They identified 25 whole-brain voxel-based morphometry studies that comprised 677 patients with ADHD (healthy controls, n=566) and 452 patients with BD-I (healthy controls, n=659), respectively. Using anisotropic effect-size signed differential mapping software, these studies compared GMV patterns between ADHD and BD-I, between BD-I and healthy controls, and between ADHD and healthy controls.

Researchers noted in the ADHD studies, there were more men in the patient cohort (61.2% vs 50.4%; P =.05), while mean age was comparable between patients and healthy controls (29.5±10.8 vs 31.0±1.2; P =.12). Mean age and sex were found to be comparable between the 79 patients with ADHD who were medication-naive and the 69 healthy controls (24.2±5.0 vs 26.2±6.6; P =.18; 83.5% vs 75.4%; P =.74).

In the BD-I studies, mean age and sex were comparable (30.6±11.1 vs 32.8±11.3; P =.26; 43.8% vs 50.8%; P =.44). Between 98 patients with BD-I in manic-state and 186 healthy controls there were more women in the patient cohort (51.0% vs 43.5%; P <.01), while mean age was comparable (25.4±6.8 vs 27.1±7.7; P =.99). There were more men in the ADHD cohort for interpatient comparison (P <.01), while mean age was comparable in interpatient comparison (P =.10).

Patients with ADHD showed smaller GMV in the anterior cingulate cortex (ACC) and supramarginal gyrus, but a larger caudate nucleus than healthy controls. In the subgroup analysis of the medication-naive group, lower GMV in the right striatum was observed.

Patients with BD-I showed smaller GMV in the orbitofrontal cortex, parahippocampal gyrus, and amygdala than healthy controls. In the subgroup analysis of the patients in manic-state, the researchers found a larger GMV in the right insula.

There were no common GMV alterations between patients with ADHD and patients with BD-I. Patients with ADHD showed smaller ACC and larger amygdala than patients with BD-I.

In subgroup analysis, insula was shown to be in patients with BD-I who were manic and was positively associated with the Young Mania Rating Scale. A positive association was observed with the ages in ADHD with decreased median cingulate cortex (MCC), and a negative association was observed with the ages in BD-I with MCC.

Limitations of the study include use of only cross-sectional data, and nonanalysis of disease course and potential medication effects.

Study authors concluded, “ADHD was closely associated with frontal-striatal and frontal-parietal circuits, and the decreased regional GMVs tended to gradually increase. BD-I was more concerned with the PFC-amygdala emotional circuit, and the abnormality seemed to continuously deteriorate.”