Studies included in analyses of plasma GABA level
| Study | Diagnostic status | Disorder state | n | Female sex, % | Mean age, yr | Main results |
|---|---|---|---|---|---|---|
| Petty et al. (39) | Unipolar and bipolar | Current MDE | 29 | NA | NA | Diminished GABA in unipolar disorder, no change in bipolar disorder |
| Petty et al. (40) | Unipolar | Current MDE | 16 | NA | NA | Diminished GABA |
| Petty et al. (41) | Unipolar and bipolar | Current MDE | 113 | NA | NA | Diminished GABA |
| Petty et al. (42) | Unipolar | Current MDE | 77 | 0 | 44.7 | Diminished GABA |
| Petty et al. (43) | Bipolar | Current MDE | 33 | NA | 41.2 | Diminished GABA |
| Paige et al. (38) | Older adults with unipolar MDE | Current MDE | 9 | 44 | 67.4 | Diminished GABA |
| Lu et. al (36) | Melancholic unipolar MDE | Current MDE | 27 | 48 | NA | Diminished GABA |
| Berrettini et al. (51) | Bipolar | Euthymic | 10 | NA | 35 | Diminished GABA |
| Berrettini et al. (52) | Bipolar | Euthymic | 49 | 44 | 35–39 | Diminished GABA in bipolar patients without lithium |
| Palmio et al. (49) | Unipolar | Before/after treatment | 10 | 70 | 56 | No GABA level change after ECT |
ECT = electroconvulsive therapy; GABA = γ-aminobutyric acid; MDE = major depressive episode; NA = not available.