Depression with Mixed Features (for DSM-5): Distinguishing Indicators Imaginary Coherence EEG Rest

Abstract

Background: The neuronal correlates of depression with mixed traits (according to DSM-5) at rest have not been studied. Objective: to determine the indicators of imaginary coherence of EEG-rest, which distinguish patients with depression with mixed features (according to DSM-5) from patients with depression without mixed features and healthy subjects, and also to trace the dependence of the identified neurophysiological characteristics on the diagnostic belonging of the symptom complex to bipolar II type or recurrent depressive disorder. Patients and methods: on a background free from drug therapy, 80 patients with depression with mixed features (XD; n = 40 — with bipolar II disorder (XB) and n = 40 — with recurrent depressive disorder (XR)), 80 patients with depression without mixed traits (TD; n = 40 — for bipolar II type (TB) and n = 40 — for recurrent depressive disorder (TR), as well as 80 healthy subjects (N). The study groups were matched by sex and age. The study used clinical-psychopathological, psychometric, neurophysiological and statistical research methods. According to the Kruskal–Wallis criterion for independent samples the parameters of imaginary coherence (modulo) of standard frequency ranges (delta (δ) — 0.5–4 Hz, theta (θ) — 4–8 Hz, alpha (α) — 8–13 Hz, beta-1 (β1) — 13–20 Hz, beta-2 (β2) — 20–30 Hz, gamma (γ) — 30–45 Hz) between pairs of 14 cutaneous standard EEG derivations (according to the “10–20” system) in three (XD, TD and N), and then in five (XB, XR, TB, TR and N) comparison groups. Post-hoc analysis was performed using the U-test. The significance level was adjusted according to the Bonferroni correction. Results: three indicators were identified: α-ICoh(C3–P4), β1-ICoh(C3–P3) and β2-ICoh(F3–C4). For all three parameters, the H-test values for the “Group” factor (n = 3 and n = 5) were highly significant. In this case, α-ICoh(C3– P4) — XD = TD, XD < N, TD < N; β1-ICoh(C3–P3) — XD < TD, XD < N; TD < N; β2-ICoh(F3–C4) — XD > TD; XD > N, TD > N. The groups of patients with XD within the framework of recurrent depressive and bipolar II disorders significantly differed in terms of β1- ICoh(C3–P3) — XR > XB. At the level of statistical trends, in type II bipolar disorder — XB > TB according to α-ICoh(C3–P4), and in recurrent depressive disorder — XR > TR according to β2-ICoh(F3–C4). Conclusion. Thus, depression with mixed features can be considered in terms of dysfunctional interactions of the left frontal, bilateral central and parietal cortical zones, depending on the diagnostic affiliation of the depressive symptom complex and reflecting violations of automatic and voluntary regulation of affect, cognitive and behavioral changes.