EEG power, frequency, asymmetry and coherence in male depression.
Level 4 - case-series / case-control
Case-control study comparing clinical patients with healthy controls
PubMed 11306251 · doi:10.1016/s0925-4927(00)00080-9
What was done
Resting, eyes-closed, vigilance-controlled 21-lead quantitative EEG recordings were collected from 70 unmedicated male outpatients with unipolar major depressive disorder and 23 healthy male controls. Spectral analysis evaluated absolute and relative power, mean frequency, inter- and intra-hemispheric power asymmetry ratios, and coherence across frequency bands. Univariate group comparisons and a discriminant function classification analysis were performed.
What was found
Depressed males showed greater overall relative beta power, as well as greater absolute beta power and faster mean total spectrum frequency bilaterally in anterior regions compared to controls. Inter-hemispheric alpha power asymmetry differed between groups, with controls exhibiting relatively reduced left hemisphere activation, and patients showing widespread reductions in delta, theta, alpha, and beta coherence indices. Intra-hemispheric theta power asymmetry was reduced bilaterally in patients across all regions, while intra-hemispheric beta asymmetry reduction was restricted to the right hemisphere. Discriminant function analysis correctly classified 91.3% of patients and controls. Exact numerical spectral values, standard deviations, and p-values were not reported in the abstract.
Why it matters
The study indicates that quantitative EEG abnormalities in male depression involve widespread disruption of intra- and inter-hemispheric synchrony alongside heightened frontal beta activity. Combining coherence and asymmetry measures demonstrates strong discriminatory capacity between depressed individuals and healthy controls.
Limits
The study included only male participants, precluding generalization to female depression. The sample size of the control group was relatively small (n = 23) compared to patients (n = 70). The abstract does not report cross-validation for the discriminant analysis, raising the potential for overfitting, nor does it report depression severity sub-analyses or longitudinal stability.
Cited by
- supports In depression, quantitative EEG demonstrates impaired interhemispheric communication and reduced information flow between the left and right frontal lobes.