White Matter Network Topologies Differ in Remitted MDD vs Bipolar Disorder

Patients with remitted major depressive disorder (rMDD) have differing white matter network topologies in multiple brain regions compared with healthy controls and patients with remitted bipolar disorder (rBD), according to findings published in Journal of Affective Disorders.

Researchers recruited patients with rMDD (n=33; 8 men; mean age, 32.667 years), rBD (n=54; 27 men; mean age, 32.259 years), and healthy controls (n=60; 25 men; mean age, 33.067 years) from the First Hospital of China Medical University, Shenyang Mental Health Center, and surrounding areas between 2009 and 2021. Study participants were evaluated using the 17-item Hamilton Rating Scale for Depression (HAMD-17) and Young Mania Rating Scale (YMRS) instruments, and underwent magnetic resonance imaging (MRI). Group differences were evaluated.

Among the rMDD and rBD groups, HAMD-17 scores were 3.242 and 2.074 points (P <.05) and YMRS scores were 1.091 and 0.907 points, respectively.

The global network efficiency, local network efficiency, all nodal degrees, all nodal efficiencies, and all nodal shortest path lengths differed significantly between groups (all P <.005).

Compared with controls, all MRI findings differed significantly for the rMDD group (all P <.05). All but the left pallidum and left inferior temporal gyrus nodal degrees differed significantly for the rBD group (all P <.05).

For the 2 patient groups, right calcarine fissure, right cuneus, left lingual gyrus, and left middle occipital gyrus nodal degrees, efficiencies, and shortest path lengths differed significantly (all P <.05).

Generally, the nodal degrees of the right calcarine fissure, right cuneus, left lingual gyrus, and left middle occipital gyrus were highest among the rMDD group and similar among the controls and rBD group. For left pallidum and left inferior temporal gyrus, the rMDD group had the highest nodal degrees, followed by the rBD and controls. Regarding nodal efficiency, the rMDD cohort had the highest and the rBD and controls had similar levels. The opposite pattern was observed for nodal shortest length, in which the rMDD group had the lowest values and controls and rBD groups had the highest values.

The study is limited by the fact that 57.6% of the rMDD cohort and 81.5% of the rBD cohort were receiving antidepressants, mood stabilizers, or antipsychotic medications.

Study authors concluded, “The increased nodal degree and nodal efficiency, and decreased nodal shortest path length in the right calcarine fissure, right cuneus, left lingual gyrus, and left middle occipital gyrus were specific to rMDD. And only rMDD displayed increased global network efficiency and local network efficiency compared to healthy controls. These rMDD-specific alterations in white matter network topologies may be the neuroimaging biomarkers to distinguish rMDD from rBD.”