OBJECTIVE: Plasma gamma-aminobutyric acid (GABA) levels have been reported to be low in some patients with major depressive disorder. Premenstrual dysphoric disorder is often associated with major depressive disorder. Therefore, the authors sought to determine whether women with premenstrual dysphoric disorder with or without prior major depressive disorder also had low plasma GABA levels. METHOD: Plasma GABA levels were measured in 27 women with premenstrual dysphoric disorder and 21 comparison women during the the mid-follicular and late luteal phases of the menstrual cycle. RESULTS: In comparison women, plasma GABA levels increased from the mid-follicular to the late luteal phase. Women with premenstrual dysphoric disorder and a past history of major depressive disorder had low plasma GABA levels during both phases. In women with premenstrual dysphoric disorder but no past major depressive disorder, plasma GABA levels decreased from the nonsymptomatic, mid-follicular phase to the symptomatic, late luteal phase. CONCLUSIONS: Decreased GABA function may represent a common biological link between subtypes of depressive and premenstrual dysphoric disorders. A trait in major depressive disorder and a state- dependent decrease in premenstrual dysphoric disorder might imply a possible continuum between the two disorders.Abstract Teaser