There may be, according to preliminary research published over the weekend by researchers from Brigham and Women’s Hospital in the journal SLEEP.

Using a novel form of magnetic resonance technology, the team, led by Dr. John Winkelman, a psychiatrist in the division of sleep medicine, discovered that some people with chronic insomnia have lower brain levels of a neurotransmitter called GABA.

GABA is the brain’s major inhibitory transmitter, meaning that it helps reduce activity in the brain’s neural circuits. Low levels of brain GABA in people with insomnia may lead to their nervous system being in high gear, both day and night. “Insomnia may be not just a disturbance of sleep but may be a 24-hour a day disorder, one of whose manifestations is insomnia,” Winkelman said.

The study is believed to be the first to link insomnia with a particular biochemical glitch. Although small – 16 people with chronic insomnia and 16 good sleepers – the study is interesting because the people with insomnia were not depressed or anxious.

Historically, psychiatrists have believed chronic insomnia – which affects about 10 percent of adults – was linked to depression or anxiety.

The fact that low GABA levels may be linked to insomnia fits with the fact that many sleeping pills such as Ambien, Halcion, Restoril, Lunesta, Ativan act indirectly via GABA receptors, perhaps by flipping a chemical switch in the hypothalamus.

Winkelman notes that, while sleeping pills can often be helpful, nondrug treatments such as cognitive behavioral therapy also can reduce insomnia.

Clifford Saper, a neurologist at Beth Israel Deaconess Medical Center who has studied this sleep-wake switch, cautions, “We are only now beginning to work out the complex circuitry in the brain that causes insomnia. There are very few studies in humans, so new data are very welcome.”