Interoception in Autism and Anorexia
Most of us know about the five basic senses: touch, taste, smell, sight, and hearing. However, there are three more, lesser-known senses that play just as critical a role in our everyday lives: vestibular, proprioception, and interoception. The vestibular system contributes to our sense of location, giving us the ability to maintain proper balance and body posture. The receptors in this system are located in the inner ear and are stimulated by changes in head position. Proprioception is responsible for the perception of our body position in space, informing us through receptors located in our muscles. It tells us whether our arm is raised or by our side, or how hard we should push that shopping cart at the grocery store to move it forward. Interoception is the sense through which we monitor the inner state of our bodies, helping us to regulate emotion and understand whether we're hungry, thirsty, in pain, too hot, or too cold.
Our interoceptive awareness is responsible for keeping our body in homeostasis, telling us to get a snack when we're hungry or go to the bathroom when our bladder is full. It balances the need for change with the need to stay the same. It is a commonly known trait of autism to lack interoceptive awareness. Parents of autistic children may notice that their child has trouble expressing their emotions, and their child may show signs of eating and toileting difficulties. What is not as highly recognized, however, is the role of interoception in eating disorders--specifically anorexia--and how a potential lack of interoceptive awareness can contribute to the onset and continuation of the illness.
Interoception and the Insula
To gain understanding as to why those with autism and anorexia often lack interoceptive awareness, it is helpful to first understand the role of the insula. The insula is a small region of the cerebral cortex located deep within the lateral sulcus, which is a large fissure that separates the frontal and parietal lobes from the temporal lobe. Although small, the insula plays a major role in our ability to navigate life, since it sends and receives messages from almost every part of the brain!
One of the insula's primary jobs is to manage interoceptive awareness. According to a 2004 neurology study, researchers found that people with better interoceptive skills have larger insulae. This poses the question whether the insula works differently in individuals with mental health issues. Knowing that our interoceptive awareness is responsible for regulating our inner cues also helps us to explain why those who lack interoceptive awareness often experience heightened anxiety, a trait that is very common across both the autistic and eating disorder spectrum. Someone who lacks interoceptive awareness may be over-responsive to inner cues of fear or worry, resulting in increased feelings of anxiety. Considering this, several studies have been conducted in recent years to unmask the way the insula may work differently in individuals with autism and/or co-morbid eating disorders. Researchers have hypothesized and found results that imply that the insula may be hypoactive in said individuals.
Interoception in Autism
People with ASD often struggle making sense of interoceptive information. Something that's supposed to tickle may hurt, and autistic individuals may not respond to feelings of hunger or thirst in a timely manner. Interoception also affects the interpretation of emotions, meaning those on the autistic spectrum may have difficulty identifying their own emotions, a trait known as alexithymia.
Interoceptive difficulties can affect one's ability to self-regulate, resulting in temper tantrums and/or meltdowns. If you don't know if you're hungry, you may wait too long to eat, causing a severe drop in blood sugar...and we all know what it's like to be around someone who's #hangry! If you need to use the bathroom but are not aware of your full bladder, you may feel uncomfortable and not understand why. When you are unable to explain what is troubling you, frustration can build up and it can be very difficult for loved ones to understand how to best help the individual affected. What can be even harder, is knowing how or when to ask for help at all, if you can't put into words what exactly is wrong.
To be honest, I had never heard about interoception until I found out I have autism. As a result of this newfound knowledge, I started educating myself about this neurodevelopmental disability and for the first time in my life, all the times I've felt "off" suddenly made sense. Also being an anorexia survivor, I began to wonder if certain autistic traits may play a role in the onset of eating disorders. It may just be me, but not properly responding to hunger signals is a common autistic trait that seems to very closely resemble one of the main symptoms of anorexia.
Interoception in Anorexia
Anorexia Nervosa has the highest mortality rate of any mental illness. It is characterized by a dangerously low bodyweight, food restriction, excessive exercise, and more often than not, co-morbid anxiety and mood disorders. Anorexia causes severe malnutrition, which affects every part of the body--including the brain.
When the body is starved, it will shut off internal processes and turn to internal organs for fuel. The body will do everything in its power to keep you alive, even if that means using brain matter as energy. This "eating" of the brain and other vital organs results in the shrinking of the insula as well as reduces blood flow to the brain. The firing of neurons requires energy and oxygen, both of which are carried by blood. Inadequate blood flow causes all parts of the brain to malfunction, which means neurons can't send messages as quickly. This results in slowing down of the rate at which the insula can process information, which helps explain why individuals with anorexia have difficulty processing interoceptive stimuli.
Simple questions such as "what do you want for dinner?" can be so overwhelming that the brain defaults to a simple answer: I'm not hungry. I already ate. These habitual answers are how we avoid what Ken Nunn refers to as analysis paralysis--overthinking things, constantly tweaking details, not being able to see what's important. We wait to tackle a problem until we find the "perfect" solution, but because no perfect solution exists, the problem doesn't get solved and you become "paralyzed" by your overthinking. Anorexia seems to be the "solution" to avoiding analysis paralysis. We can't figure out the "perfect" food to eat, so we don't eat at all. It's too complicated to break our rigid exercise and meal routines, so we stay stuck.
The insula also plays a role in feelings of disgust. It's a primal emotion that's often reserved for life-threatening situations such as coming into contact with spoiled food or bodily waste. However, in a study observing disgust sensitivity in eating disorders, researchers found that someone with anorexia may be disgusted by any food.
People with anorexia have trouble sensing and responding to hunger signals, both of which are regulated by our interoceptive awareness through the insula. This weakness in interoceptive skills may help explain why so many people with anorexia fail to perceive the severity of their illness. Known as anosognosia or feeling like you're not sick enough, is seen in several mental illnesses including anorexia, schizophrenia, bipolar disorder, and some stroke patients. The interoceptive deficits simply cause someone with anorexia to be less or even unaware of the physical signs of the illness.
Perhaps the most prominent relationship between interoception (or rather, lack thereof) and anorexia lies in the realm of body dysmorphia. Neuroscientist Manos Tsakiris of the University of London defines body image as "a conscious representation of what we look like", or how we picture ourselves in our heads. Most of the time, this picture is quite accurate. In those with eating disorders, I think anyone reading this knows that is (most often) not the case. According to a 2020 study at Anglia Ruskin University, researchers surveyed over 1,600 participants, 30% of which had disordered eating. 76% of those who indicated an eating disorder or a history thereof, had co-morbid body dysmorphic disorder(s). So why is it that those with the genetics for anorexia also seem to have a deluded self-image?
From the outside, it doesn't seem like having trouble sensing whether you're hungry or whether or not you have to go to the bathroom could cause body dysmorphia. However, looking at your body in the mirror is only one aspect of how body image is formed. Tsakiris concludes "someone with high interoception will place more weight on proprioception and inner feelings, while someone with low interoception might place more weight on visual cues". This indicates that those with low interoceptive awareness are more dependent on external cues.
Tsakiris tested this hypothesis using the Rubber Hand Illusion. Although this may sound like a magic trick you'd see at a carnaval, this experiment allows neuroscientists to observe the connection between body and mind.
The Rubber Hand Illusion
In 1988, psychologists Botvinick and Jonathan Cohen asked ten healthy subjects to place both hands on the table in front of them. They then placed a screen on the inside of the left arm, parallel to the arm, to hide the person's left hand from view. Immediately to the right of the screen, Botvinick and Cohen placed a realistic, life-sized rubber hand. Then, they began simultaneously stroking the subject's left hand and the rubber hand with a small paintbrush. After a minute or two of brushing, something unusual happened; the subjects began to feel as if the rubber hand was their own. Their body image had spontaneously morphed to exclude their real left hand and replaced it with a lifeless rubber hand instead.
To measure the relationship between interoception, body image, and the Rubber Hand Illusion, Tsakiris and colleagues asked a group of 46 neurologically healthy undergraduate women to complete a heartbeat test. Based on the results of this test, the women were split into high and low interoception groups, in which their mean estimated heart rate was 81 percent and 49 percent accurate. The women were then given questionnaires to assess body image and participated in the Rubber Hand Illusion. Women in the high-intensity group were less likely to report feeling that the rubber hand had become part of their body.
The results of the rubber hand illusion provides the first direct evidence of the role that interoception plays with regards to experiencing body image from the outside.
Have you ever received a body comment, only to believe it with your heart and soul? The phenomenon of viewing your own body from a third person's perspective in called allocentrism. Normally, the body provides plenty of information about its internal states to negate allocentrism, but in anorexia this information isn't there. Lack of interoceptive awareness impairs the ability to perceive oneself from a first-person perspective, which is directly linked to lacking internal cues. Because the internal cues are not fully present, people with anorexia fail to perceive the physical manifestations of weight loss and can therefore persist with the life-threatening habits of starvation and over-exercise much longer than someone without the genetic predisposition. Italian researcher Giuseppe Riva calls this persistent self-objectification in eating disorders "allocentric lock". This allocentric lock is amplified by anxiety, a co-morbid disorder in over two-thirds of anorexia patients.
A classic example of allocentric lock is captured in the way an individual with anorexia may internalize an external body comment, as mentioned above. Personally, I have never seen myself as fat. Even at my lowest weight, I was deathly aware of how skeletal I looked. But as I started to gain weight and people made comments such as "you look so healthy!" I immediately started to doubt whether or not I still had to gain weight. I know this specific example may not be as extreme as someone who is severely underweight and yet, perceives themselves as morbidly obese, but it goes to show that allocentric lock and lack of accurate body image *literally* comes in all shapes and sizes.
How can you improve your interoceptive awareness?
Those of us with autism and anorexia may have a different brain make-up and struggle with processing interoceptive information, but it's obviously not a free card to not eat. Although we may not have the capacity to achieve the same function of someone with a normally functioning insula, there are several techniques proven to aid in improving interoceptive awareness. These include mindfulness techniques such as yoga, meditation, visualization, and focused breathing.
I hope this blog gave you insight and helped you gain a better understanding of yourself or perhaps someone you care deeply for and I'd love to hear what you thought! Send me a message on Instagram or via my contact form! Messages with feedback always mean the world to me ❤️
Interoception in Anorexia Nervosa: Exploring Associations With Alexithymia and Autistic Traits https://pubmed.ncbi.nlm.nih.gov/32153442/
The Role of Interoception in the Pathogenesis and Treatment of Anorexia Nervosa: A Narrative Review https://pubmed.ncbi.nlm.nih.gov/32362843/
Neural systems supporting interoceptive awarenesshttps://pubmed.ncbi.nlm.nih.gov/14730305/
Where Mind and Body Meet https://www.researchgate.net/publication/253952210_Where_Mind_and_Body_Meet
Decoding Anorexia by Carrie Arnold https://amzn.to/3cAr5Gq
Disgust sensitivity in eating disorders: A preliminary investigation https://pubmed.ncbi.nlm.nih.gov/10744851/
Alexithymia in women with anorexia nervosa. A preliminary investigation https://pubmed.ncbi.nlm.nih.gov/1521107/
The association of interoceptive awareness and alexithymia with neurotransmitter concentrations in insula and anterior cingulate https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4040102/
Early-onset anorexia nervosa: Is there evidence of limbic system imbalance? https://www.researchgate.net/publication/10836281_Early-onset_anorexia_nervosa_Is_there_evidence_of_limbic_system_imbalance
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From the body's viscera to the body's image: Is there a link between interoception and body image concerns? https://pubmed.ncbi.nlm.nih.gov/28377099/
Movement and the rubber hand illusion https://www.researchgate.net/publication/24375394_Movement_and_the_rubber_hand_illusion_Perception_38_271-280
Comorbidity of anxiety disorders with anorexia and bulimia nervosa https://pubmed.ncbi.nlm.nih.gov/15569892/
Neuroscience and eating disorders: the allocentric lock hypothesis https://pubmed.ncbi.nlm.nih.gov/22100628/
Interoception and Autism: Body Awareness Challenges for Those with ASD https://autismawarenesscentre.com/interoception-and-autism-body-awareness-challenges-for-those-with-asd/
Anterior cingulate cortex and insula response during indirect and direct processing of emotional faces in generalized social anxiety disorder https://pubmed.ncbi.nlm.nih.gov/23547713/
Interoception and sensory processing issues: What you need to know https://www.understood.org/en/learning-thinking-differences/child-learning-disabilities/sensory-processing-issues/interoception-and-sensory-processing-issues-what-you-need-to-know