Can too much sleep cause depression, or does depression cause hypersomnia? Not that this is an age-old riddle, but little time and effort have been put to the answer. Part of the reason for that neglect is that sleep has been viewed as something that merely happens to us, as opposed to something we do… passive versus active participation. It’s odd, though, that when we really try to fall asleep, we can’t.
One misconception about sleep is that it’s a simple mechanism. Nope. It’s a complex cascade of events that involves the chemistry of excitation, inhibition, blocking and parrying, all in order to convince the body that it’s getting sleepy. GABA (gamma-aminobutyric acid), for example, tries to block the stimulators that keep us awake by slowing the activity of nerve cells in the brain, while caffeine blocks the receptors that cause drowsiness. All this arguing among the neurotransmitters barely warrants a mention, despite that sometimes we can seem asleep while awake and at other times, just the opposite.
During sleep, the will and consciousness are suspended for a time, body functions slow down, and we remain (relatively and reversibly) immobile. At first we drift in and out, ready to stir if need be. In a minute, we begin non-rapid-eye-movement sleep (NREM), which is the dreamless period during which brain activity is low but of high voltage. Here, heart rate and blood pressure are low (and regular). At this point, it’s hard to awaken. During REM sleep, brain waves are fast but of low voltage. Heart rate and respiration are irregular. Now we dream and exhibit rapid eye movements. This accounts for about one quarter of total sleep, occurring four or five times a night. As with any other scientific, health-related topic, theories about REM sleep are plentiful. One that has a following declares that creativity and problem solving skills are embellished during this stage of respite (Wagner, 2004), but are likewise inhibited if deprived of the phase (Carskadon, 2011). One thing we know for sure is that the body can’t regulate temperature during REM sleep, so that abnormally hot or cold temps can interrupt it, fouling up our timing the next time we doze off, and putting us into REM sleep right away in an effort to catch up. Antidepressants and heavy smoking can gum the works, too. Many smokers are light sleepers.
Circadian rhythm is the inborn biochemical cycle responsible for the integration of sleep with external clues, namely light and darkness. It’s naturally longer than twenty-four hours, but earth’s rotation says it’s twenty-four. Changing the optical input, as happens to people living in Alaska, can force circadian rhythm to use other cues to coordinate sleep time, some of which are contrived to create darkness during daylight. Regardless, we need GABA activity and normal metabolism of norepinephrine, serotonin, epinephrine and histamine.
Inability to stay awake, termed hypersomnia, affects about five percent of the populace, having significant impact on the daily routine. Causes are many and varied, and run the gamut from neurological to endocrinological to infectious to respiratory (Dauvilliers, 2005). But an association of hypersomnia to depression is not easy to relate because of the complexity of the issue and the possibility of being bidirectional. While mood aberrations might cause a person to sleep a lot, there’s not much evidence that too much sleep can cause a mood disorder (Dauvilliers, 2013). Those with sleep disorders may or may not be depressed (Ohayon, 2008).
An alarming result of a Korean study reported that middle school students deprived of sufficient sleep because of psychological/behavioral issues held suicidal ideations that worsened with weekend oversleep and weekday shortage of sleep, leading to the conclusion that sleep restriction among disaffected adolescents increases risk for self-destructive behaviors. (Lee, 2012). That sleep disturbances are common in depressed persons is also seen in children so affected. In fact, the more depressed the child, the more severe the sleep abnormality, characterized by insomnia or hypersomnia, or both (Liu, 2007).
In a longitudinal study of young adults conducted in the mid 1990’s, investigators found that insomnia occurring every day for more than two weeks could be a predictor of subsequent depressive states (Breslau, 1996) (Gillin, 1998). This may not have been borne out definitively by later investigations, but becomes food for thought in the presence of prolonged, unexplained sleep disturbances.
For those with diagnosed depressed affect, antidepressant medications can compound sleep problems, largely by inhibiting REM sleep and causing insomnia. Afterward, extreme tiredness will invite hypersomnia, and begin an unwelcome cycle. Swapping drugs for natural modalities to address perturbed affect on the one hand and poor sleep habits on the other hand might offer insight into treating both areas of individual equilibrium. In most instances, sleeping too long is not likely to make you depressed. However, being late for work is another story.
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