The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning (43 page)
Authors: Daniel Bor
BOOK: The Ravenous Brain: How the New Science of Consciousness Explains Our Insatiable Search for Meaning
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UNHEALTHY SLEEP, UNHEALTHY CONSCIOUSNESS
While autism may be unique in being a disorder of an overabundance of awareness, most other psychiatric conditions may be caused by a shrunken and skewed consciousness. And for a surprising proportion of these patients, part of the cause of a diminished awareness is a simple source that could be easily corrected: sleep disruption.
I feel very lucky that I’ve never had a mental illness. Whether or not it’s related in my case, I’m also, as long as I keep the espresso drinking down, a solid sleeper. But it doesn’t take much sleep deprivation for me to catch a glimpse of what some mental illness sufferers endure. In my student days, I had my fair share of nights with little sleep because of looming assignment deadlines, or more social reasons. If, on rare occasions, there were two nights in a row with less than a few hours’ sleep, I felt like a different person—very much for the worse. I saw myself as temporarily half-senile. I seemed to be suffering from amnesia for the little, yet important, details, like computer passwords or the names of my friends. I struggled to perform simple actions, such as cooking a meal, and my mind generally seemed to be in a perpetual fog. I became far more anxious, more prone to stress, and less confident than usual. Most striking of all, two days with little sleep and I approached the edges of hallucination. I didn’t hear alien voices in my head, see imaginary people in front of me, or anything else that dramatic. On a frighteningly regular basis, though, I could no longer be sure whether or not my name had been mentioned in a nearby conversation between complete strangers, or whether the pattern in the carpet had started moving of its own accord. Unlike those with a real mental illness, I was constantly reassured by the fact that one good night’s sleep would instantly cure me. But for so many people, that is simply not an option.
Sleep and dreams are a pervasive and bizarre part of our lives: We spend about a third of each and every day semi-comatose in our beds, deliberately reducing consciousness either to a near void of experience or to surreal, disconnected vignettes locked inside our heads. The world’s most popular drug, caffeine, is enjoyed mainly for its ability to ward off feelings of sleepiness. Deprive us of the land of nod for just one night and we immediately develop profound impairments in cognition. Deprive us for two or more nights, and we may begin to show transitory signs of psychosis. After 48 hours, we will find it almost impossible to fight the desire to sleep. This is in surprising contrast to something as seemingly vital as food.
Brought up in a religious Jewish household, I am no stranger to fasting. The Day of Atonement, Yom Kippur, involves a total fast of food and water for 25 hours or so (though no such sleep fast is included). I remember one Yom Kippur when I was eleven. Under the rules, I needn’t have fasted until I had passed my thirteenth birthday. At this stage, my religious views were already starting to dissolve into atheism, but ever the scientist, my curiosity for mini-personal experiments was already quite apparent, so I insisted on fasting to see what it would feel like and how I would cope. By midafternoon, I’d already been fasting for about 19 hours, with no water or food at all. At this point, with a group of friends, I secretly ducked out of prayers to play a game of soccer in a deserted hall on the far side of the building. Running around for an hour is not the most sensible option when you are probably somewhat close to dehydration, but I seemed to be no worse for the activity, and was struck when the fast was broken that evening during dinner by how easy it had been to go without sustenance for an entire day.
In striking contrast, I don’t think I’ve ever gone without sleep for a full 24 hours and not had to struggle desperately by the end of it to stay awake.
Experiments in rats indicate that total sleep deprivation for up to a month is consistently fatal. Almost all animals sleep, including insects. Most scientists believe that our ability to nod off, and especially to dream, is a key ingredient in effective learning and memory. Single neurons, it appears, can become overused and “tired” in the day; they need a period of reduced activity to reset themselves and become ready for a new period of learning tomorrow. Sleep is one of the prices we pay for flexible, information-hungry brains.
Therefore, if we want a trim, smoothly running consciousness, we need healthy periods of peaceful slumber. This connection between sleep and health might not be the most earth-shattering scientific revelation, but nevertheless it is a fact we all too readily ignore. In the teeth of our stressful, busy modern lives, we all regularly underestimate how delicate sleep can be and how profoundly it can affect our mental health.
Humans probably top the animal kingdom in the sheer range and prevalence of sleep problems we collectively endure—just as we top the animal kingdom in the range of psychiatric and neurological illnesses we are prone to. Common sleep disorders, unfortunately, are another of those payments we have to make for such a complex brain and such a broad, supercharged consciousness. It’s been known for decades that sleep problems are associated with a host of psychiatric conditions. But the conventional wisdom was always that sleep problems were a symptom, rather than a cause, of psychiatric disorders. Now that assumption is increasingly being turned on its head.
On the surface, determining whether sleep difficulties cause, or are the effects of, mental illness is a tricky issue to disentangle: A person on the cusp of a depressive episode might feel a spike in stress because of her debilitating feelings, and the stress might keep her up at night, which will make her more stressed, anxious, and upset, and the downward spiral continues. But in fact, there are methods to bypass this confusion.
Sleep-related breathing disorders cause profound sleep disruption, usually without the slumbering person realizing there are any problems, even for many years. The most prevalent kind, sleep apnea, normally manifests as pauses in breath as frequently as every few minutes throughout the night as the windpipe becomes blocked. This pseudo-suffocation forces the person to wake up for a moment, but normally not long enough to remember the event the next morning. Crucially here, the cause rarely has to do with the brain, and instead usually arises from mechanical deficiencies in the throat. Paul Peppard and colleagues examined whether sufferers of this condition would be more likely to have depression, and this is indeed what he found, with the risk of depression related to the severity of the breathing problems. In other words, merely having chronic, poor-quality sleep can induce depression.
Closely related to this is seasonal affective disorder (SAD), a form of depression that rears its debilitating head in the winter months when there is less daylight around. Its sufferers feel generally sleepy, lacking in energy, and low in mood—almost as if they have half entered into hibernation (which might well be what is occurring, as an evolutionary remnant of some earlier mammalian form). The main, commonsensical treatment for this condition is light therapy, where patients sit near specially designed lamps as a substitute for the sunlight they are missing. The effect of this treatment is to raise alertness levels, which at the same time helps blast away those blue feelings.
Attention deficit hyperactivity disorder (ADHD) is a childhood condition with even more obvious links to sleep and consciousness. Admittedly, this condition is, in some people’s eyes, a rather amorphous and vague catalog of symptoms, which allows for dangerous overdiagnosis, medicalization, and management via potentially addictive drugs. Still, it’s clear that a subset of children labeled as ADHD have a serious disorder, with a genetic basis, that makes them disruptively impulsive, hyperactive, and unable to concentrate, with a shriveled working memory. The fact that working memory, the mental playground of consciousness, is diminished is itself a good indicator that consciousness is lower. And sleep is likely to be one of the causes of this, as again shown by sleep apnea.
David Gozal and colleagues found that five- to seven-year-old children were considerably more likely to have symptoms of ADHD if they had sleep apnea. Although the most pronounced ADHD children didn’t show this relationship, possibly because their symptoms were already being generated by underlying genetic abnormalities, their sleep was still far from normal: Their rapid eye movement (REM), or dream-period, sleep was significantly curtailed and commenced later in the night than in normal children. This portion of our night’s sleep is the most important for learning and memory. If we have a poor night’s sleep, the proportion of our REM sleep the next night increases to catch up. Disturbances in REM sleep have also been spotted in depressives and schizophrenics.
If you’ve ever witnessed a child at the end of the day who is overtired but also strangely excitable—and more likely to misbehave—this emerging picture of ADHD as akin to a chronic lack of sleep may make considerable sense. ADHD sufferers can report almost feeling like zombies, as if they are only semiconscious but are automatically doing all they can to overcompensate for this awkward state. Supporting this view, the prefrontal parietal network, the key network for consciousness, is chronically underactivated in ADHD children.
You might think that to combat hyperactivity, doctors would prescribe valium or low-dose sedatives to cajole these patients’ minds into a quieter, more serene state. Instead, as if in tacit acknowledgment that these patients are permanently overtired, stimulants such as Ritalin are ubiquitously used for ADHD.
As some of my wife’s symptoms suggested, bipolar disorder can compete with ADHD for its ties with sleep. For instance, manic episodes are far more likely if a bipolar sufferer is forced to miss a night of sleep, or flies into a different time zone, thus unbalancing the sleep-wake cycle.
In fact, in almost any major mental illness, the ties between disturbed sleep and psychiatric symptoms are becoming increasingly clear. For instance, abnormalities in genetic and molecular processes that regulate sleep have been linked with unipolar depression, seasonal affective disorder, bipolar disorder, mania, panic disorder, post-traumatic stress disorder, obsessive compulsive disorder, ADHD, and schizophrenia.
If many of these conditions relate to chronic under-awareness in normal waking life, then it stands to reason that stimulants, whose purpose is to increase arousal, may be of benefit in relieving symptoms. As mentioned above, this is the conventional treatment for ADHD in the form of Ritalin, but what of other conditions? One of the clues that led my wife to stimulant medication to treat her bipolar disorder was that she had clearly been, for many years, self-medicating on lots and lots of coffee during the day. This was the only method she had to feel better. It turns out, perhaps unsurprisingly, that coffee has a rather robust protective effect against depression for many women (so far, the main studies have not included men). For instance, Ichiro Kawachi and colleagues demonstrated, quite convincingly, that coffee intake prevents suicide. And another recent study by Michel Lucas and colleagues showed that increased coffee drinking is associated with a lower incidence of depression. Psychiatrists seem slowly to be turning toward the medical forms of stimulants as effective alternative treatments for many psychiatric conditions, but an accelerated push in this direction may be warranted in order to yield more breakthroughs.
Another emerging weapon in the clinical arsenal to correct sleep problems and raise alertness in mental illness is light therapy. While it’s well known that this treatment is very effective against seasonal affective disorder, it has also been shown to help in all manner of psychiatric conditions, including any form of depression, ADHD, and even Parkinson’s disease and other forms of dementia.
In short, a quiet revolution is building in psychiatry, where sleep abnormalities are viewed as an important potential cause of mental illness rather than another symptom. And treatments are starting to target the fact that in these patients sleep quality needs to be improved and daily arousal levels increased.
WORKING MEMORY NOT WORKINGWhile the evidence is mounting that a paucity of wakeful consciousness can cause an array of mental illnesses, the question remains as to why exactly this could turn some people into psychiatric patients, as opposed to simply feeling tired. As the model defended in this book asserts, a reduced awareness relates closely to a reduced working memory capacity. This in turn can lead to less mental control, a lower ability to innovate your way out of trouble, and a smaller chance that you’ll notice when your thinking or behavior may be moving in dangerously wrong directions.
What is the evidence that sleep problems actually shrink your working memory? The evidence for children comes from observing their natural day-to-day sleep quality and seeing how this relates to working memory. A poorer quality sleep does indeed impair performance on a range of working memory tasks. In healthy adults, you can be manipulative rather than observational, forcing an entire night of sleep deprivation and then monitoring the effects both behaviorally and in the fMRI scanner. Michael Chee and Wei Chieh Choo carried out such a study and found that a lack of sleep created both working memory problems and a less efficient prefrontal parietal network than normal. In this study, healthy volunteers in their early twenties missed just one night’s sleep and effectively had brain activity that resembled that of seventy-year-olds. Robert Thomas and colleagues, studying adults with sleep apnea, found very similar results to the sleep deprivation study just mentioned. Fragmentary sleep in this patient group was associated both with a slowing of performance and reduced accuracy in a verbal working memory task, as well as a reduction in prefrontal cortex activity.
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