In a study sponsored by the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, researchers looked at the seemingly paradoxical phenomena of patients with depressive illnesses experiencing improved moods after experiencing sleep deprivation. The findings were published in the Proceedings of the National Academy of Sciences (PNAS).
The study discovered that in both healthy and depressed people, one night of complete sleep deprivation increased amygdala connection to the cortex of the anterior cingulate, which was associated with improved mood.
The impact of total sleep deprivation (TSD) on state of mind and functional connectivity systems was investigated in sleep deprivation experiments involving healthy people (n=38), patients with severe depression (n=30), and 16 unassisted sleep-deprived controls.
The studies were conducted for five days at the University of Pennsylvania Hospital’s Clinical Translational Research Centre lab. Three rs-fMRI scanning sessions were performed on all subjects. Per participant, 210 fMRI pictures were collected.
Over the five days, participants had three resting-state fMRI scanning sessions. The baseline scan was performed in the early hours of day two following a typical night’s sleep. The TSD group participants who had not slept the night before underwent a second scanning session the following morning.
Following two nights of sound sleep, individuals underwent their final scan session on the morning of the fifth day. Every two hours from days two to five, everyone who participated completed a 37-item condensed version of the Profile of Mood States. As anticipated, most subjects displayed a decline in mood right away after sleeping less than usual. After one night of TSD, 13 out of 30 (43%) depressed patients reported improvement, whereas the remaining 17 experienced a worse or no change.
Twenty subjects with major depressive disorder reported mood improvement after one night of sound sleep, while the remaining 20 reported mood deterioration or no change. Patients with better moods had considerably higher connections between their amygdala and anterior cingulate cortex than those with worse moods. The amygdala, which processes threatening or fear-inducing inputs and signals other brain regions for a reaction action, is the center of the fight or flight response.
The “cognitive” prefrontal cortex and the “emotional” limbic system are both connected to the anterior cingulate cortex (ACC). It has a significant impact on, among other things, our capacity to govern and regulate our emotional states.
According to the research, the amygdala-ACC network connection could be a viable target for antidepressant therapies since it may reflect brain resilience to mood alteration following sleep loss. According to the researchers, the duration of rapid eye movement (REM) sleep may be one possible explanation behind the individual variability in the TSD effect.
REM sleep disorders have previously been linked to major depression. In the middle frontal lobes, which are made up of the ACC and the prefrontal cortex in the middle, too much REM sleep would reduce noradrenaline, which would lead to less binding to the -2 receptor. Some participants may benefit from a break from REM sleep during TSD because it improves top-down control over the amygdala, which has an antidepressant impact.
