Winkelman JW et al. (2008) Reduced brain GABA in primary insomnia: preliminary data from 4T proton magnetic resonance spectroscopy (1H-MRS). Sleep 31: 1499–1506

Evidence from human and animal studies has suggested a role for γ-aminobutyric acid (GABA) in the etiology of primary insomnia. This theory is supported by a recent study that used proton magnetic resonance spectroscopy (1H-MRS) to measure GABA levels in the brains of volunteers; individuals with primary insomnia had lower GABA levels than normal sleepers.

Winkelman et al. recruited 16 nonmedicated volunteers with primary insomnia and 16 controls. Global brain GABA levels were calculated as an average of levels from 1H-MRS measurements of the basal ganglia, thalamus, temporal, parietal and occipital white matter, and cortex. Individuals with primary insomnia had GABA levels that were, on average, 30% lower than the levels in normal sleepers. The GABA:creatine ratio was 0.18 in insomniac volunteers, compared with 0.25 in controls. In polysomnography studies of participants with insomnia, the occurrence of waking >45 min after sleep onset correlated inversely with GABA levels. Across all study participants, self-reported sleep quality correlated positively with GABA levels. Age, sex and BMI did not influence GABA levels.

The authors conclude that 1H-MRS is a valuable means of assessing GABA levels in vivo. In combination with other MRS acquisition techniques to enable resolution of regional differences in GABA levels, such methods may help to elucidate the relationship between GABA levels and insomnia.