Today, we are going to talk about hallucinations. Quite straightforward, don't you think? Well, in medicine, patients who are presented with hallucination can be quite complicated especially if we seek to understand the exact mechanism of it. Too many diseases can cause hallucination and the first thing that comes to mind when we are talking about this kind of psychopathology is, of course, psychiatric illnesses. Not everyone has the luxury (well, I wouldn't call it a luxury though) of experiencing voices, creeping sensation or seeing something, hmm, how should I put it, things that are not from this world (ghost, apparition, angel and such), so most of us don't understand, how it feels like to perceive something that is not even there. In everyday conversations, sometimes, people use the word "delusion" (most common) or "illusion" when they actually meant hallucination. Even though it might appear the same for a layman, all of those three words are quite different; well to be fair, delusion is quite different from the other two. Hallucination is a perception without apparent stimuli while an illusion is an inappropriate perception to the existing stimuli (for example, a child might perceived curtains as ghosts at night), so it is understandable if someone confused illusion with hallucination.
Delusion is an unshakable belief which is held with utmost convictions despite evidence to the contrary. The false beliefs which are perceived by delusional people are usually out of keeping with the usual cultural and social norms. For example, in persecutory (paranoid) delusion, people who were delusional insist that they were being followed, spied or pursued by a serial killer which, in reality, doesn't exist. In some cases, people who are delusional claimed that their life partners were cheating on them, allegedly, so they went for extra measures of spying, hiring a spy or checking their husband/wife clothes for some evidence of their infidelity; which is essentially non-existence. Most of the delusional patients that I have seen in a clinic have poor insight and they were often treated with a cocktail of mixed therapies comprised of any of the antipsychotic, antidepressant and probably some mood stabilisers. Being delusional is the primary feature of a paranoid schizophrenia and without proper treatment and adherence to medications, they can be very difficult to live with. Imagine living with someone who suspects every single thing that you do will eventually harm them in some possible ways. It's tiring, really.
In this series, however, we are not going to discuss either delusion or illusion. In this article, we are going to discuss some introduction to hallucinations. It is important for you to understand even if you experience a somewhat similar presentation to a specific diagnosis included in this series, it doesn't necessarily mean you have it. Hallucination is not pathognomonic (specific) to a certain disease so it would be a great idea for you to refer yourself to a psychiatrist if you are experiencing hallucinations; some healthy people often misinterpret their symptoms as hallucinations even though it is not. Even if it is not diagnostic, most of the cases of hallucinations are studied through patients who have been diagnosed with schizophrenia. It's not that surprising since schizophrenia is the hallmark of psychiatric illnesses; people with schizophrenia can literally present with any of the symptoms found in other psychiatric illnesses. Still, it would be appropriate for us to use the latest guideline to diagnose schizophrenia or we will end up seeing schizophrenia in every single individual.
To be honest, I'm not an expert in neurobiology nor will I be in the next 5 years or so, thus, this section of discussion is purely based on what I read in some review journals that have been published; if you have disagreements or some insights to the discussion, I welcome your opinion in the comment section, below. It is important to know that, everyone, including healthy people, could experience hallucination; though the experience can be quite different from what people with a specific medical condition went through. In 2009, data from 6 different countries yielded between 7 to 30% of healthy children and adolescents who have experienced some form of hallucinations without any medical condition or risk factors to be affected by it. The result was proven to be true by a study conducted by Scott J. et al which stated that despite all of the possible clinical correlations or demographics, adolescents might be the most frequent population of healthy subjects who experienced hallucinations.
Apart from idiopathic causes, people who lose someone (death) could experience hallucinations (mostly visual) related to the deceased as a part of their grieving process. People's mind is a powerful tool of survival and pathological grieving could trigger a defence mechanism which would allow people to see someone they desire (deceased) to curb their sadness from leading them to unwanted consequences; though ironically, this defence mechanism eventually would cost them later. Most of the studies that are conducted to investigate the source of hallucinations came from people with schizophrenia so it is not known whether appropriate to assume it is the same for other diseases as well. Obviously, the commonest type of hallucination is different between psychiatric and organic problems; in psychiatric illnesses, the most common type of hallucination would be auditory. Other forms of hallucinations such as gustatory, visual or tactile are usually caused by organic diseases though that doesn't rule out psychiatric illnesses; one thing I hate about medicine, there is no definite answer for some questions.
In individuals with good mental health, the most common cause of hallucination is brain lesion. Compared to delusions, hallucinations are quite easy to be recognised even by someone who knows but is not familiar with the subject; the trick is to add the word "might" in front of your statement. You heard someone see, hear or feel something that is not there, well, they might be hallucinating. Most of the brain lesions that have resulted in hallucinations were found to affect pathways associated with sensory modalities related to the type of hallucinations (i.e. visual pathway, somatic pathway, auditory pathway). One of the best examples would be patients who experienced a condition called Charles Bonnet Syndrome (CBS). In this condition, people who can't see (completely or partially blind) by eye's condition such as cataract, diabetic maculopathy or glaucoma, experienced visual hallucination as if their visions are perfectly normal. The degree of severity varies but some patients claimed that they can see perfectly what has been going on around them for a moment, and when we asked them to describe the experience, most of them are too good to be true or bizarre. The thing about images that are projected due to CBS, you can't control or manipulate them; the brain is provided with a false sense of sighting experience which can't be manipulated in any way imaginable. Listen to the story from a patient who experiences CBS in the video below.
It is, therefore, reasonable to assume that hallucinations presented in patients with schizophrenia can be quite different from people who experienced hallucinations from other diseases. Most of the studies which utilised the latest technology of neuroimaging have produced comprehensive pieces of information regarding hallucinating brains. Although most of them are studied among patients with schizophrenia, the basis of hallucination is thought to remain the same regardless of the causes of the hallucination itself. In patients with schizophrenia, it was found that auditory hallucinations can potentially be caused by a reduction of grey matters in some areas of the brain which are responsible for the perception of sounds (or other respective area associated with the type of hallucinations); this is the most common and consistent findings and it almost resembles the brain of people who are drunk with alcohol (though it might be much more significant for an alcoholic). This would lead to a bad connectivity termed as faulty frontotemporal interactions which are important for a normal social interaction and language perception; a faulty frontotemporal communication would cause patients to perceive false external stimuli which are interpreted internally (faulty internal signal generation).
It is best for you to note that this is the most frequent finding when people with schizophrenia experienced hallucinations. This psychopathology is still poorly understood and most of the treatment modalities focused on treating the disease itself thus the hallucination; there are up until now, no medication which caters to hallucinations alone. Some medications or drugs can induce hallucination, especially in an abuse setting making it a popular choice among people to escape reality by letting the brain to construct a world which is non-existent, filled with things that can't manipulate or be manipulated. Most of the animal studies suggested that medications that can cause psychosis in humans would alter their behaviour in a certain way in which we can differentiate, either they act based on either thing of their surrounding or from themselves. In other words, behavioural changes among animal who received medications (source of psychosis) would be similar with when they perceived sounds/visuals are coming from the other animal (in this case, there are no other animals nearby, they were hallucinating). Nevertheless, behavioural changes caused by hallucinations in animals are too nonspecific making it unreliable predictors whether or not they were hallucinating. It is undeniable that more studies are needed to understand the thing which might have caused hallucinations.
Waking up in the middle of the night can be frustrating especially if you are clinically depressed. Apparently, there is no amount of melatonin that can maintain your sleep when you have a high level of cortisol, swimming around your circulation. Even more so, if you woke up and found that you can't move, only your eyes kept on blinking and for a few seconds, gaze upon your whole visual field; the experience can be traumatic. Sleep paralysis is a common unexplained disorder that can be somewhat distressful especially for those who aren't aware of this condition. People would usually resort to a paranormal reasoning first when they were freaking out, unable to move and probably, for some, saw something sitting on their body. Studies in the past found that some people (40% of the general population) would eventually experience sleep paralysis that would make their life miserable at some point in their life. It is unclear what is the exact mechanism that causes temporary paralysis, but researchers thought that it occurs due to an accidental awakening while we are in the rapid eyes movement (REM) phase of the sleep cycle. Neat isn't it?
During the REM phase, our muscles become paralysed to prevent us from acting out whatever we are dreaming about. Obviously, sleep paralysis indicates that at some point, we are aware of our surrounding, but our body doesn't even know that we have woke up. Being paralysed can be physiological for a healthy individual who sleeps it off through the REM cycle but for people who experienced sleep paralysis, this would disrupt a part of the brain which holds neural map information of the body. We became confused, clueless and scared despite our brain best effort to try and configure some instruction for the limb to move. One interesting thing about that particular part of the brain (people assume it is the parietal lobe) it holds information regarding our body images which could have leaked and projected as hallucinations; in other words, the "thing" that was sitting on us is our own self-reflected images. It seems plausible to consider the "thing" to be paranormal since they looked distorted but not all of the images' information was projected and interpreted as external stimuli. According to Baland Jalal, the only way to test this hypothesis is to conduct an experiment on people who have different body images for example amputee. In this case, the "thing" that sits on their body would appear amputated as well.
Due to a poor understanding regarding the pathophysiology of sleep paralysis, it is quite difficult to explain to laymen that this condition wasn't caused by paranormal entities. In 2013, a study was conducted in two different societies [most people are religious (Egypt) and most people are atheist (Denmark)] to investigate the relationship between stresses imposed by cultural beliefs and the rate of sleep paralysis. It was found that people from Egypt experienced a much intense and prolonged sleep paralysis as compared to people who are from Denmark. When asked, people from Denmark believe that sleep paralysis was caused by brain malfunctions while nearly half of the Egyptians claimed that such condition was caused by a spirit called Jinn (or Djinn). If people who believe that supernatural entities were the primary cause of the disorder, the reason for their prolonged episode of sleep paralysis can potentially be "fear". However, like any other hypotheses, a lot of things need to be considered before jumping to a definite conclusion. Hallucinations are quite complicated and it is possible that different diseases exhibit a different mechanism or pathway that would eventually lead to hallucination.
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