Cortical GABA levels in primary insomnia.
OBJECTIVE
GABA is increasingly recognized as an important neurotransmitter for the initiation and maintenance of sleep. We sought to measure cortical GABA content through proton magnetic resonance spectroscopy (MRS) in persons with and without primary insomnia, and relate brain GABA levels to polysomnographic sleep measures.


METHODS
Two-group comparison study.


METHODS
Outpatient study at a university research clinic.


METHODS
Non-medicated persons with primary insomnia (N = 16) and no sleep complaints (N = 17).


METHODS
Participants kept sleep diaries and a regular time-in-bed schedule for 9 days, culminating in 2 consecutive nights of ambulatory polysomnography and a single proton MRS session. The main outcome measure was occipital GABA/creatine ratios; secondary measures included sleep measurements and relationship between polysomnographically measured time awake after sleep onset and occipital GABA content.


RESULTS
The primary insomnia group was distinguished from persons with no sleep complaints on self-reported and polysomnographically measured sleep. The two groups did not differ in age, sex, body mass index, habitual bed- and wake-times, napping, use of caffeine, or use of cigarettes. Mean occipital GABA level was 12% higher in persons with insomnia than in persons without sleep complaints (P < 0.05). In both groups, GABA levels correlated negatively with polysomnographically measured time awake after sleep onset (P < 0.05).


CONCLUSIONS
Increased GABA levels in persons with insomnia may reflect an allostatic response to chronic hyperarousal. The preserved, negative relationship between GABA and time awake after sleep onset supports this notion, indicating that the possible allostatic response is adaptive.
Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA. peter.morgan@yale.edu
Peter T
PT
Morgan
Edward F
EF
Pace-Schott
Graeme F
GF
Mason
Erica
E
Forselius
Madonna
M
Fasula
Gerald W
GW
Valentine
Gerard
G
Sanacora
D000328:Adult; D001923:Brain Chemistry; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D007319:Sleep Initiation and Maintenance Disorders / Q000378:metabolism* / Q000503:physiopathology; D005680:gamma-Aminobutyric Acid / Q000032:analysis*
D005680:gamma-Aminobutyric Acid