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Sleep-deprived amygdalas fire 60% harder
In people who had a full night of sleep, the amygdala showed a controlled, modest degree of reactivity. In sleep-deprived people, the reactivity was amplified and almost aggravated. It is as though, without sleep, the brain becomes all emotional gas pedal with too little regulatory control brake.
That neurological signature is not dissimilar to numerous psychiatric conditions. Significant links have been found between sleep disruption and depression, anxiety including PTSD, schizophrenia, and suicide. No single psychiatric condition has been found in which sleep is normal.
How does the amygdala generate emotion?
The amygdala is an almond-shaped cluster of neurons in the temporal lobe. It rapidly flags things that may matter for survival, such as threats, and triggers the body's stress response through the hypothalamus. It also tags emotional experiences so that they are remembered more strongly. Damage to it in animals and people dulls fear responses.
What keeps the amygdala in check?
The medial prefrontal cortex, behind the forehead, sends calming signals to the amygdala and helps regulate its output. In a 2007 study in Current Biology, Seung-Schik Yoo, Matthew Walker, and colleagues scanned volunteers after sleep deprivation. They found the amygdala reacting far more strongly to upsetting images and its connection with the prefrontal cortex weakened. This is the basis of the brake comparison.
How strongly is insomnia linked to depression?
A 2011 meta-analysis led by Chiara Baglioni in the Journal of Affective Disorders pooled data from longitudinal studies. People with insomnia at the start had about double the risk of developing depression later, compared with people who slept normally. The pattern runs in both directions. Depression also disrupts sleep.
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