Jul 11 2011

Sleep Paralysis

Recently I received the following e-mail:

Thank you so much for your show. The other night your podcast saved me from a night full of stress and fear. I woke up in the middle of the night after a nightmare not being able to move and started hearing voices. My eyes were wide open, I could see that everything was normal but kept hearing a voices asking me to go to bible studies. After five minutes of freaking out I remembered sleep paralysis stories from you show and realized what was happening to me. I rode the strange voices out for an hour just realizing my mind misfiring and not having a spiritual awakening.

I have heard similar stories from other readers/listeners and also my patients. I have also had similar experiences myself (always when sleep-deprived). They can be quite frightening and unpleasant. A typical episode of sleep paralysis, or hypnagogic (when falling asleep) / hypnapompic (when waking up) hallucinations includes the feeling of being paralyzed combined with a sense that there is a malevolent presence in the room. Often there is also the sense of pressure on the chest, as if it is difficult to breathe or even that something is sitting on your chest. There may also be auditory and visual hallucinations to complete the package. The situation is scary enough, but there also appears to be an element of spontaneous terror as well.

Now imagine you are a typical person living in the middle ages or in any similar culture – without the benefit of modern neuroscience to help you make sense of this event. It is a profound experience, outside of our normal everyday experience. It is no surprise that pre-scientific cultures developed myths to explain these occurrences, especially since about 15% of the normal population will at times experience sleep paralysis episodes. (They are also common in sleep disorders, like narcolepsy).

In Scandanavia they have a legend of the “sea hag” who visits people at night to steal their essence. In Europe there are stories of the succubus or incubus- demons that visit people in their sleep to engage in unholy conjugal acts. In more modern times ghosts are more common than demons. I have heard it argued that ghost steal energy from you while you are sleeping so that they can manifest themselves, and that is the reason for the paralysis.

Another modern explanation for these episodes is alien abduction. The little gray aliens paralyze their targets before either bringing them aboard their ship, implanting devices, or probing various orifices.

Again – it is not surprising that such fanciful explanations develop to explain these episodes. We are used to assuming that our brains are accurate recorders of external reality. Our first assumption when we experience something is that it really happened, as we experienced it, not that our brains are malfunctioning.

Now, however, we have knowledge of the brain’s function and many of the ways in which it is flawed and can generate false experiences. Sleep paralysis is just one dramatic and common example. In normal sleeping a center in our brainstems will inhibit the descending motor pathways – they will paralyze you below the neck. This is so you don’t physically act out your dreams. Your eyes can still move, however, so you do exhibit rapid eye movement (REM), which has become an important marker for dreaming.

While in the dream state you are also dreaming – your brain is generating an internal story which can be quite compelling and seems real, at least to our dreaming selves. What I have described above is best understood as a waking dream, a fusion of the dreaming and waking brain states. The body is still paralyzed and the brain is still generating a dream, but it is mixed with reality – so the experience can seem real, as if we are awake. It is a waking dream.

Understanding this is empowering, in that we do not need to be afraid that we were just visited by a demon or hag or that we are being probed by aliens. Some people who experience sleep paralysis think they are going insane. I have had several patients who were very happy and reassured to hear that they were just experiencing a known and benign neurological phenomenon, not something supernatural and not a sign of mental illness.

The waking dream phenomenon is an excellent example of how understanding the world, and in particular ourselves, through the process of science gives us tremendous explanatory power. This reduces the need to invent superstitions or supernatural explanations for seemingly weird occurrences.

Further – waking dreams are yet another example of why we cannot fully trust our brains. Our brains are capable of distorting, filtering, and interpreting sensory input, of altering memories and even generating false memories, and of generating false experiences. While it is good enough for everyday activity, our brains have many flaws. We cannot rely upon our memories of our experiences to understand the world, especially when those experiences are unexpected or unusual. We need external verification, objective measurement, and careful recording of data.

In other words – we need science and skepticism to compensate for the flaws and pitfalls of our neurobiology.

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