Outcome | Group; mean ± SD | |
---|---|---|
Pre-rTMS | Post-rTMS | |
Overall sample (n = 26) | ||
GABA, IU | 2.0 ± 0.4 | 2.2 ± 0.4* |
Grey matter, % volume | 46.8 ± 5.5 | 48.4 ± 5.6 |
White matter, % volume | 36.0 ± 8.3 | 33.5 ± 8.9 |
CSF, % volume | 16.8 ± 4.9 | 17.7 ± 5.6 |
TMS responders (n = 12)† | ||
GABA, IU | 1.9 ± 0.4 | 2.3 ± 0.3* |
Grey matter, % volume | 48.3 ± 5.0 | 50.1 ± 5.1 |
White matter, % volume | 32.9 ± 6.0 | 29.5 ± 6.0 |
CSF, % volume | 17.9 ± 3.2 | 19.8 ± 4.4 |
TMS nonresponders (n = 14)† | ||
GABA, IU | 2.0 ± 0.4 | 2.1 ± 0.4 |
Grey matter, % volume | 45.5 ± 5.8 | 47.0 ± 5.8 |
White matter, % volume | 38.5 ± 9.2 | 36.9 ± 9.8 |
CSF, % volume | 15.9 ± 5.9 | 15.9 ± 6.0 |
CSF = cerebrospinal fluid; DLPFC = dorsolateral prefrontal cortex (middle frontal cortex); GABA = γ-aminobutyric acid; IU = institutional units; MRS = magnetic resonance spectroscopy; rTMS = repetitive transcranial magnetic stimulation; SD = standard deviation.
↵* p < 0.05: repeated-measures analysis of variance (accounting for use of GABAergic medication and TMS stimulation hemisphere) for overall sample, or post hoc protected t test of the a priori hypothesis of post-TMS GABA elevation for the TMS responder subsample.
↵† Responder status based on ≥30% reduction in the 30-item Inventory of Depressive Symptoms score after rTMS treatment.30