Sleeplessness causes psychiatric disorders

27 October, 2007

A few sleepless nights will not only make one tired and groggy but also may lead to “rewiring of the brain’s emotional circuitry.” The result: the brain will be put into a primitive “fight or flight” state.

Already, numerous studies conducted all over the world over several decades have linked lack of sleep to ailments ranging from disruptions in the immune system to cognitive deficits to weight control.

Research done by a team led by psychologist Matthew Walker, of the University of California, Berkeley, the United States, found that almost all psychiatric disorders show some problems with sleep.

The study has been published in the journal Current Biology.

Scientists previously believed that the psychiatric problems triggered the sleep issues. However, Matthew Walker said, the new research conducted by his team suggests that the reverse is the case – that is, a lack of sleep causes certain psychological disturbances.

Matthew Walker’s team and collaborators from Harvard Medical School reached their conclusions after studying 26 healthy students aged 24 to 31 after either an all-nighter or a full night’s sleep.

In all, 14 subjects spent 35 straight hours without getting a wink before they were put under functional magnetic resonance imaging (fMRI) scanners where their brains were observed while they viewed a set of 100 photos that became increasingly disturbing as they progressed.

The early slides shown were snapshots of an empty wicker basket on a table. The scenes changed as the series progressed to more shocking settings, such as a tarantula on a person’s shoulder. Finally, pictures of burn victims and other traumatic portraits were shown to them.

The researchers mainly monitored the amygdala, a midbrain structure that decodes emotion, and observed that both sets of volunteers had a similar baseline of activity when shown the inoffensive images. But, when the scenes became more gruesome, the amygdalae of the sleep-deprived participants increased, showing 60% more activity relative to the normal population’s response. Also, the researchers noticed that over five times more neurons in the area were transmitting impulses in the sleep-deprived brains.

Matthew Walker described the heightened emotional response in those exhausted as “profound,” adding, “We have never seen a magnitude of increase between two groups that big in any of our studies before.”

The research team also checked the MRI readings to determine whether any other brain regions had a similar pattern of activity, which would indicate that the brain networks were communicating with one another.

In normal participants, the amygdala seemed to be talking to the medial prefrontal cortex, an outer layer of the brain that, according to Matthew Walker, helps contextualise experiences and emotions. However, in the sleep-deprived brain, the amygdala seemed to be what he called “rewired” instead with a brain stem area called the locus coeruleus, which secretes norepinephrine, a precursor of the hormone adrenaline that triggers “fight or
flight” reactions.

Robert Stickgold, an associate professor of psychiatry at Harvard Medical School who was not involved in this study, said he believes that “there seems to be a causal relationship between impaired sleep and some of the psychiatric symptomatology and disorders that we’re seeing.” He cited as examples the research linking sleep apnea – in which breathing is disrupted – to attention-deficit hyperactivity disorder and the evidence of a connection between depression and insomnia.