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Sleep deprivation gives a lot of people a buzz. Especially in the first night of staying up, many people experience euphoria. Indeed, sleep deprivation can even be a short-term way to address depression. The effects of depression decline. Total sleep deprivation for a whole night improves symptoms in 40-60% of patients. (In their manic periods people with bipolar disorder do not sleep much and do not need much sleep.) Unfortunately, sleep restriction is not a viable treatment for depression on an outpatient basis. Supervision is required.
Imaging research has shown that one night of sleep deprivation leads to an increase in brain dopamine levels. Dopamine is sometimes called the “pleasure neurotransmitter” because of its role in so much human behavior. Drugs that increase dopamine levels tend to increase wakefulness, so the increase in dopamine may be a mechanism by which the sleep deprived brain partially counteracts the effects of sleepiness.
Scientists using functional magnetic resonance imaging techniques found that sleep deprivation “amplifies reactivity” of parts of the brain in response to positive emotional stimuli. The researchers were able to identify specific parts of the brain that are affected – and there are more than a few parts – and found that the biological changes matched subjective reports of what stimuli the test subjects judged as pleasurable. The mesolimbic dopamine pathways are made more sensitive. The neurological substrates of sleepiness remain incompletely understood, but this work shows brain changes that support the observation of euphoria in sleep deprived patients and the findings that many depressed people can get a short-term boost in mood by staying up past their bedtimes.
Scientists have also found that a type of neuron called glial cells are important here. Glial cells called astrocytes release neurotransmitter adenosine while we are awake. This is part of the homeostatic process of sleep regulation and a build-up of adenosine makes us sleepy. (Caffeine counteracts adenosine.) A study in mice concluded the adenosine was likely the cause of the antidepressant effects of staying awake a long time. The researchers think this may open the way to finding antidepressant medications that work through different biochemical pathways from the ones available now.
Researchers were quoted in the press expressing the concern that lack of sleep by people in jobs requiring judgement. If they experience this euphoria, their judgment could become impaired and lead to poor decisions. The sleep-deprived brain is liable to mood swings that increase the risk for bad decisions, according to the lead investigator.
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