By Dr. Michelle Garnett and Professor Tony Attwood
We know that autism is a risk factor for both mental and physical health conditions. One study (Lever & Gertz, 2016) found that up to 79% of autistic adults met diagnostic criteria for a mental health condition, including depressive, anxiety and eating disorders. We also know that many autistic individuals struggle to emotionally self-regulate (use internal strategies to calm down, like breathing) and to co-regulate (be soothed by another person), so they find other ways to self-soothe or feel OK, and one example is by eating or not eating.
Sensory sensitivities are extremely common in autism, so much so that they form part of the diagnostic criteria (APA, 2022). Eating involves all five senses and interoception, or the capacity to sense internal bodily sensations such as hunger and satiation. It is perhaps unsurprising that eating disorders are overrepresented in the autistic population. In this article we discuss the prevalence of eating disorders in autism, why this is the case, and why it is important to routinely screen for autism in clinics that treat eating disorders, and to carefully assess the possibility of eating disorders in clinics that specialise in neurodiversity, including autism.
Prevalence of eating disorders in autism
The eating disorders most associated with autism are anorexia nervosa, Avoidant Restrictive Food Intake Disorder (ARFID) and Pica. A recent study found that up to 35% of women in an inpatient unit for anorexia nervosa (AN) are likely to be autistic, based on a screening questionnaire, compared to 20% in the outpatient unit and 2% in the general population (Tchanturia, 2021).
ARFID has only recently been added to international definitions of eating disorders (APA, 2022) and estimates of co-occurring ARFID and autism range from 12.5% to 33.3% (Harris et al., 2019; Inouye 2021), compared to 1.5% in the general population. Pica is diagnosed when the person persistently eats non-food substances for over 1 month. Pica is more commonly associated with autism than with any other condition.
Bulimia nervosa and binge-eating disorder occur most often in individuals with ADHD, due to difficulties resisting the impulse to binge or to purge. However, we know that autism and ADHD commonly co-occur with a recent meta-analysis showed the range across 63 studies of between 40 and 70% (Rong et al, 2021) and studies are increasingly recognising an ‘autism-ADHD phenotype’ (Craig et al, 2016). This association of autism with ADHD, the lack of studies on bulimia and binge-eating disorder in autism, and that it is common to experience another eating disorder across the lifetime if one has already experienced one (e.g. Eddy, et al 2013) are factors that encourage us to screen for bulimia and binge-eating disorder in autistic individuals, in addition to AN, ARFID and Pica.
Possible pathways to an eating disorder if you are autistic
One of the diagnostic criteria of being autistic is having a sensory system that works differently (APA, 2022). This means that an autistic person is more likely to have hyper or hypo sensitivities for the taste, texture, sight, sound, and smell of food. One pathway to an eating disorder is the different sensory system, leading to restrictive eating practices to avoid certain sensory experiences, for example, experiencing the look of many types of food as being disgusting, or the texture, taste or smell as intolerable. Conversely sensory seeking behaviours can lead to overeating certain types of food for the sensory experience, for example, adoring the taste of sweet food, or foods of a certain texture or “feel” in the mouth.
We also know that autistic individuals experience differences in interoception, or the perception of internal body sensations. For some autistic people, the sensations of feeling food in the body, sensations of digestion, bloating, nausea, or constipation, are intolerable, and therefore eating is meticulously avoided as much as possible. There can also be difficulties interpreting the feelings of hunger and fullness, leading to problems of under eating initially, but then overeating because the person only registers feeling hungry when they are ravenous, and then does not feel full until they have eaten too much. Without the internal cues of hunger and satiation, the person may struggle to establish a regular eating routine.
The person may enjoy the feeling of being ‘empty’, that is having no food in them, and feeling lighter. The choice to restrict food is to pursue this enjoyable sensory experience.
Unfortunately, many autistic individuals in our society experience loneliness (Henriksen et al 2017), bullying, and abuse (Rumball, 2019). They may use restrictive eating patterns as a way of distracting themselves from these difficulties, and to numb the emotional pain. As one autistic person with anorexia nervosa said, I could get engrossed in food and exercise, and just forget about everything else.
Conversely, they may use comfort eating to overcome difficult feelings associated with socialising. Many social occasions are paired with eating. Socialising can be difficult and anxiety-provoking for an autistic person. It is difficult to eat when you are overwhelmed and anxious. The beginnings of an eating disorder may be traced to avoidance of eating in social situations, and then enjoying the resulting consequences of not eating. For example, the sensory experience of being ‘empty’ or ‘light,’ or the experience of losing weight, or avoiding feeling nauseous.
Self and identity
Eating disorders often begin in puberty, just as the social world becomes more complex and the autistic person experiences more problems navigating changing social expectations and trying to connect with their peers and ‘fit in.’ They often feel very different from their peers and may become immersed in an eating disorder as a way of coping. They may believe that they do not fit in socially because of their body or their appearance, so seek to change both. It is common for teenagers to connect with peers through a common interest, but an autistic teenager may not be able to connect with the interests of non-autistic groups. As they become more fascinated with eating disorder behaviours, they may become accepted in a peer group that embraces this culture. Some autistic teenagers will focus on dieting and appearance as a way of being included, and to build a sense of identity.
Sometimes restrictive eating can commence because the person seeks to remain asexual and androgynous, fearing change and disliking the body changes that start to occur due to puberty. For example, the person may be afraid of becoming an adult and the changes this will bring to their lives, feeling incapable of getting a job or living independently, and so may seek to stay in their childlike body.
Disliking and resisting pubertal body changes can also be related to gender dysphoria, for example, when a teenage girl intensely dislikes growing breasts, and developing a feminine physique, so ceases eating to try to stop the process.
Traumatic interpersonal incidences including rape and sexual assault occur more often to autistic people (Kerns et al 2016). Either increasing or decreasing body weight may be chosen as a strategic defence against any future sexual harassment or abuse. Excess weight can be seen a defence, a barrier to a predator, and being under-weight can be a way of seeming asexual or non-sexual.
We have found that autistic people often experience difficulties discerning the character or personality of others, including their own personality. They often define themselves in terms of their interests and knowledge, rather than in terms of personality descriptors or social roles, such as mother, daughter, or friend. This difficulty with conceptualising the self can lead to over-reliance on a self-definition in terms of physical appearance, including their weight, rather than their character and personality qualities.
Children and teenagers can find out early on in their life that they can regulate their emotions by controlling their food intake. In childhood there are few other options for this. We hope that the child can regulate themselves through co-regulation, that is they are able to seek support and comfort from a primary caregiver. Sometimes, due to the social difficulties in autism that can affect family relationships, the autistic child may prefer to self-regulate alone. They may simply not think to seek the comfort of a parent, or they may dislike the offered comforts, such as a hug or increased physical contact, or talking about the problem. When trying to self-regulate alone does not work, they can seek other methods, including restricting their eating, eating non-food substances (Pica) or over-eating certain foods. Restrictive eating often leads to emotional numbness, which is seen by an autistic person as a positive outcome. Overeating can be experienced as soothing and comforting. One of the reasons for Pica may be a sensory seeking behaviour to block an uncomfortable or painful emotion.
Intolerance of uncertainty can be a trigger to dieting or food restriction. As life becomes more complicated, with the increased changes and transitions of high school, and increased social expectations in the adolescent years, there is a considerable level of uncertainty. Controlling one’s food intake and exercise output can be a coping mechanism against the high levels of anxiety that come along with uncertainty. As one autistic adult said, I highly value predictability and consistency. One way I can achieve this in my life is by controlling what I eat, and how many calories I burn.
Part of the international definition of autism is rigidity in thinking (APA, 2022). Once an autistic person has made a decision, they can be very determined and stay with the decision, despite data and persuasion to the contrary. For example, the person may decide that their life is far easier and simpler if they follow the rules dictated by the eating disorder and are therefore very reluctant to change.
There are other types of thinking that are characteristic in autism and may be a risk factor for developing an eating disorder. For example, black-and-white thinking. The person may think if I am not thin, then I am fat, and sees weight as a dichotomy, rather than a range of acceptable weights. They can stick very rigidly to a single number on the weighing scale, as being the only desirable number, even though that number puts them at a life-threatening weight. Part of the rigidity of thinking can be what we have called in the past the “Frank Sinatra Syndrome”, or “My Way”. Once the person has decided on their beliefs about their weight, the rules around their eating and exercise patterns, they can be very rigid. They are not open to other people’s advice or opinions, even if these are based on scientific evidence.
An autistic person tends to be a systematic thinker, very good at recognising patterns and devising systems. They can be very attracted to a systematic way of eating and managing weight, where they can easily establish and have clear rules to follow about what to eat, how much to eat, and how much exercise to engage in.
Enthusiasms and passions
One of the qualities of autism is the intensity of the interests the person can develop, and the pleasure that these interests bring. One of the reasons eating disorders can develop is because of an intellectual fascination with eating and its effect on the body, as well as the numbers involved, for example in terms of calories for different foods. They may enjoy exploring eating patterns, rules, and weight. They may keep schedules and spreadsheets or use Apps to record progress. Entering numbers and seeking patterns can be a very enjoyable aspect of their interest. The eating disorder practices become a source of enjoyment, and they embrace being an expert in the eating disorder. Their expertise and commitment are admired by others with an eating disorder. Social media can be a way of sharing their knowledge and gaining dopamine through the number of ‘likes’ achieved on their social media page.
Why screen for autism in eating disorder clinics and hospitals?
There is gathering evidence that it is helpful for autistic people to know that they are autistic, to increase their own self-understanding, self-acceptance, and recovery from mental health disorders (Bradley et al, 2021, Harmens, Sedgewick & Hobson, 2022). Specifically related to eating disorders, Professor Kate Tchanturia, Lead Clinical Psychologist for the National Eating Disorder Service, UK, and Professor in the Psychology of Eating Disorders at Kings College, London, says that the first ‘take-home message’ from all the research to date is that knowing the person is autistic is helpful when treating eating disorders. As she says, “If we can ‘see it,’ we can ‘say it’…. and we can ‘sort it,’ to support people with both conditions” (p.16, Tchanturia, 2021). There is research to show that adjusting treatment of eating disorders to accommodate the characteristics of autism, not only increases the success of the treatment, but also decreases the cost of delivery of the treatment (Tchanturia, et al 2021).
As Pooky Knightsmith said:
The label gave my treatment team permission to revise the way they treated me, and to realise that sometimes we had to turn the typical approach on its head in order to make progress with me. The label also helped me to begin to understand myself and helped me to make sense of a lot of the difficulties I’ve faced day to day my whole life. Being able to view myself through this new lens was incredibly helpful and allowed me to be a little kinder to myself and to begin to rethink my approach to many things. The label also gave me a community I could identify with and an avenue into learning, how best to support myself day today (p. 37, Ch. 3 Anorexia and Autism, Tchanturia, 2021).
Why screen for eating disorders in clinics that specialise in autism and ADHD?
Being autistic means that developing an eating disorder is more likely than if you are not autistic. Many eating disorders are secretive, and therefore hidden from view and the autistic person or person with ADHD may not tell their clinician that they are suffering in this way. In anorexia nervosa the eating disorder is ego-syntonic, that is, it is experienced as being a part of or the whole of their self-identity, but they are aware that a psychologist may wish to assist them to recover from an eating disorder, so they will hide their disorder.
Anorexia Nervosa carries the highest mortality rate of any mental health disorder at 10-20%, with suicide and the effects of starvation being the key causes of death respectively (Bernstein, 2023). The burden on the family for anorexia nervosa is higher than for schizophrenia or depression (Martin et al, 2015). Mortality rates are 1.9, 3.8, and 1.5 times higher than for an age-matched sample for bulimia, Eating Disorder Not Otherwise Specified (EDNOS) and binge-eating disorder respectively (Quadflieg, Strobel & Naab, 2019, Fichter & Quadflieg, 2016). In addition to mortality and family burden there are other costs, including that “quality of life is reduced, yearly healthcare costs are 48% higher than in the general population, the presence of mental health comorbidity is associated with 48% lower yearly earnings, the number of children is reduced, and risks for adverse pregnancy and neonatal outcomes are increased” (p. 521, Van Hoeken & Hoek, 2020).
Accurate diagnosis of an eating disorder with neurodiversity in a neurodivergent person will lead to more accurate interventions and support for these conditions, and therefore, better outcomes. These better outcomes include saving people’s lives and helping them and their families lead happier and more fulfilled lives.
Where to from here?
As clinical psychologists, we have been working with autistic individuals with eating disorders for a combined 80 years and have discovered some important ways to help. In our upcoming event, Eating Disorders and Autism, we will be sharing these with you, along with important recent research in the area. The event was created for parents and carers, autistic adults with eating disorders, as well as health and educational professionals who see people (whether they are neurodiverse or eating disordered or not because they may be either or both).
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