It’s a known fact that sleep deprivation can precipitate mania in people with bipolar disorder. Even one night of total sleep deprivation can destabilize mood to the point where hospitalization is needed. Why does this happen and what can you do about it?
To understand the relationship between sleep and mood, you need to understand a little about chronobiology (from khronos, the Greek word for time), the science of bodily rhythms and biological clocks. Nearly every living thing has an internal biological clock; even organisms as simple as bacteria have an internal time-keeping mechanism. Humans are no different.
An important concept in chronobiology is that of circadian rhythms. The term comes from the Latin words circa, meaning “around,” and diem, meaning “day.” It refers to rhythms in the body that have an approximately 24-hour cycle, like the day-night cycle. Many bodily functions follow a circadian rhythm: body temperature cycles daily as does blood pressure. It has been demonstrated experimentally that our biological clock has a natural cycle of about 25 hours and needs to be reset daily by environmental cues called zeitgebers, a German word meaning “time-givers,” that tweak our internal clock every morning to keep us on a 24-hour schedule. Although our cycle can respond to these daily tweaks without any trouble, this “reset” can shift by only about one or two hours at a time. If the zeitgeber suddenly starts arriving several hours off schedule, as happens with jet lag, it takes several days for the cycle to catch up. During that time, we awaken and get sleepy at the wrong times and generally feel out of sorts. Eventually, our internal clock adjusts, but the farther we’ve traveled, the longer it takes: about one day for each hour of time change. What happens to people whose internal clocks are out of sync with their environment for more prolonged periods?
English researchers set out to investigate this question in the late 1990s. For this experiment, healthy volunteers entered experimental living quarters where they lived on a 30-hour day: 20 hours of wakefulness, 10 hours of sleep. Every several hours while awake they took a 10-minute battery of psychological tests and rated their mood. To determine what time it was for the volunteers' biological clock, they recorded their body temperature every few hours.
For these volunteers, living on a 30-hour cycle was the equivalent of traveling through five time zones every day; their internal clocks could never catch up. The researchers found that the volunteers’ internal clocks went in and out of synchronization with their artificially-imposed sleep-wake cycle and that the more out of synchronization they were, the worse their mood became. It was the interaction of the two cycles that seemed to make the most difference. They felt worst when their internal clock was telling them it wasn’t time to get up yet and their environmentally enforced sleep-wake cycle was telling them it was time to start winding down from a long day. The more out-of-sync they were with their environment, the worse their mood became. The researchers proposed that “temporal alignment between the sleep-wake cycle and the [internal] circadian rhythms affects self-assessment of mood in healthy subjects.” Put more simply: When our sleep-wake cycle and our internal clock are out of synchronization, it has a deeply negative effect on our mood.
Even relatively minor sleep disruptions can be destabilizing for bipolar patients. When about 200 bipolar subjects were followed for a year and their sleep and mood was evaluated every several months, those with fewer hours of sleep in the prior week had more manic symptoms. Those whose sleep patterns varied widely from one night to the next had more depressive symptoms.
Brain imaging studies have shown that sleep deprivation causes disrupted communication within the mood control network of the brain in healthy individuals that is strikingly similar to that seen in persons with bipolar disorder. These healthy volunteers reported irritability and emotional volatility, symptoms not so different from those of mania. For bipolar disorder patients, then, sleep deprivation acutely exacerbates problems in mood circuitry that are already there.
Getting a better night’s sleep means taking active steps to protect your biological clock from disruptions in the environment by 1) Going to bed and getting up the same time every day, and 2) limiting exposure to light at the wrong times. For most of us, that light comes from the ubiquitous screens of 21st-century life: TV screens, computer screens, phone and tablet screens. The latter are especially problematic because they are enriched with blue wavelengths. As far as your biological clock is concerned, playing a computer game at 10:00 PM is like walking outside on a bright sunny morning with a lovely blue sky, essentially giving your brain a strong signal that it’s time to wake up—not get ready for bed.
Diane Boivin, Charles Czeisler, Derk-Jan Dijk, Jeanne Duffy, Simon Folkard, David Minors, Peter Totterdell, and James Waterhouse, “Complex Interaction of the Sleep-Wake Cycle and Circadian Phase Modulates Mood in Healthy Subjects,” Archives of General Psychiatry 54 (1997): 145–52.
Gruber, J., Miklowitz, D. J., Harvey, A. G., Frank, E., Kupfer, D., Thase, M. E., Sachs, G. S., & Ketter, T. A. (2011). Sleep matters: sleep functioning and course of illness in bipolar disorder. Journal of affective disorders, 134, no. 11 (2011): 416–420.
L. Palagini, C. Bastien, D. Marazziti, J. Ellis, D. Riemann. “The key role of insomnia and sleep loss in the dysregulation of multiple systems involved in mood disorders: A proposed model.” Journal of Sleep Research 28 (2019) e12841.