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The Diagnostic Difficulties
Chronic pain is quite common in autism, yet it is often unrecognised (and undiagnosed). The diagnosis of chronic pain in autistic individuals poses unique and intricate challenges due to various factors.
Overlap of autism symptoms with pain signs
The overlap between autism symptoms and pain indicators can lead to the misinterpretation of pain signals. Careful consideration and comprehensive assessments are necessary to differentiate pain-related behaviours from typical autistic traits. Sensory processing differences impact how autistic individuals experience pain (Ortiz Rubio et al. 2023).
Kalingel-Levi et al. (2022) investigated various aspects of pain as perceived by autistic adults, such as physical pain experience, pain sensitivity, pain awareness, pain-related emotional aspects, and pain communication; direct and indirect coping strategies; function and participation outcomes. The study found that pain awareness and communication play an important role in the pain experience of autistic people, significantly influencing their coping strategies, functioning, and participation.
Atypical pain expression in autism
One of the main reasons for the underdiagnosis of chronic pain in autistic individuals is the atypical presentation of pain symptoms. Not all autistic individuals express physical discomfort in typical ways (such as crying, moaning, or seeking comfort), which may lead medical professionals to misinterpret these behaviours as pain insensitivity. This misinterpretation can result in inadequate pain management and care.
Studies have shown that ASD individuals exhibited greater facial and behavioural pain responses during painful medical procedures (Tordjman et al. 2009; Nadar et al. 2004). Tordjman et al. (2009) hypothesised that the different modes of pain expression in individuals with ASD may be mediated by:
(1) verbal communication impairments,
(2) deficits in non-verbal communication and body image issues (e.g., difficulty locating the painful area),
(3) cognitive problems such as:
difficulty establishing cause-effect relationships between the pain sensation and the stimulus causing the pain,
problems discriminating, representing, and identifying sensations and emotions, which involves abstraction and symbolisation capacities.
challenges in learning socially appropriate responses to pain.
Numerous anecdotal reports indicate that caregivers often describe unusual, or absent, responses to painful stimuli in their autistic children. Some parents can even describe unique behaviours that indicate when their child is in pain. (However, it is important to note that altered pain expression is not universally observed in all individuals with ASD.)
The pain experiences of autistic individuals occur along a spectrum of severity, and the experience and expression of pain may differ depending on where the person lies on this spectrum (Messmer et al. 2008). Factors such as the level of communication and language abilities and the impact of different ASD diagnoses (e.g., Asperger's disorder, PDD-NOS)[1] can also influence pain expression and reactivity. This variability emphasises the need for individualised interventions and treatments.
Pain reactivity vs. pain sensitivity
It is important to distinguish pain reactivity from pain sensitivity and not to assume that absence of behavioural pain reactivity means an absence of pain sensitivity. Despite a high rate of absent behavioural pain reactivity during venepuncture, ASD individuals displayed a significantly increased heart rate in response to venepuncture. This strongly indicates that prior reports of reduced pain sensitivity in ASD are related to a different mode of pain expression rather than insensitivity or endogenous analgesia.
Plasma beta-endorphin levels were higher in the ASD group and were positively associated with ASD severity and heart rate before or after venepuncture, but not with behavioural pain reactivity (Tordjman et al. 2009). The findings also show that a significant proportion of ASD individuals did not display low/absent overall pain reactivity according to the parental, caregiver, and blood drawing evaluations. In fact, the majority (78%) of ASD individuals were found to exhibit normal behavioural reactivity to burning, highlighting the importance of distinguishing different types of painful stimuli; 22% displayed normal behavioural pain reactivity to venepuncture, and 15.9% displayed hyperreactivity. This study suggests that there may be different subgroups within the ASD population: one subgroup may experience pain insensitivity, another pain sensitivity, and the other normal pain sensitivity.
Pain perception and anticipation
Gu et al. (2017) examined pain perception and anticipation in high-functioning autistic adults and matched controls using an anticipatory pain paradigm combined with functional magnetic resonance imaging and concurrent skin conductance response recording. ASD participants showed greater activation in both the rostral and dorsal anterior cingulate cortex during the anticipation of stimulation but not during stimulation delivery. These results suggest that ASD is marked by an aberrantly higher level of sensitivity to upcoming aversive stimuli, reflecting abnormal attentional orientation to nociceptive signals and a failure in interoceptive inference.
Communication barriers in pain reporting
Autistic individuals may have difficulty communicating their pain levels or symptoms, leading to underdiagnosis and undertreatment of chronic pain conditions (e.g., Hadden et al. 2000; Stallard et al., 2001). Healthcare providers need to be attuned to nonverbal cues and alternative communication methods to ensure that pain is not overlooked. Self-reporting of pain can be challenging for individuals with communication difficulties or atypical sensory processing, such as children with ASD.
An objective method to identify discomfort would be valuable for individuals unable to express or recognise their bodily distress. Near-infrared spectroscopy (NIRS) is a brain-imaging modality suited for this application. Schudlo et al. (2021) evaluated the potential of detecting a cortical response to discomfort in the ASD population using NIRS. Their findings suggest that NIRS may serve as a tool for objective pain assessment and for understanding atypical sensory processing.
Medical bias and diagnostic delays
The common belief that autistic children have lower pain sensitivity compared to non-autistic children may influence how observers interpret pain expression and behavioural reactivity in these children, leading to an underestimation of pain and inadequate pain management.
Parents, caregivers, and mental health professionals have reported that some children with ASD appear to withstand painful stimuli (bumps, cuts, etc.), show an absence of nociceptive reflexes (e.g., absence of hand withdrawal reflex when burning oneself), or lack protective body positioning in cases of broken limbs (Tordjman et al. 2009). However, nearly all of the support for this notion of pain insensitivity is derived from anecdotal reports and limited clinical observations (Panksepp 1979; Frescka & Davis 1991; Sher 1997; Mieres et al. 2011).
Common co-occurring conditions impacting pain diagnosis
Individuals with autism often experience co-occurring conditions that can complicate pain diagnosis. For instance, the findings of Garcia-Villamisar et al. (2019) showed that greater autism severity predicted greater pain response, which was partially mediated by anxiety and depression. These data suggest that mental health symptoms are important when considering pain response in autism. It is also difficult to determine how much of the observed pain reactions are due to the autistic individual's level of distress rather than any pain response.
A study by Tordjman et al. (2009), showing greater behavioural responses in autistic children, also found higher levels of a physiological marker for stress in the ASD sample. This indicates the possibility that increased behavioural reactivity may not be an expression of pain; rather, they may be distressed by undergoing a medical procedure. Addressing these comorbidities in conjunction with pain assessment is vital for comprehensive care.
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The lack of awareness and understanding of chronic pain in individuals with autism can have far-reaching consequences on their overall well-being. Untreated chronic pain can lead to increased levels of stress, anxiety, and depression, as well as difficulties with sleep and daily functioning. This can further impact social interactions, communication, and participation in activities, ultimately affecting the individual's quality of life. It is important for healthcare providers to have a better understanding of the unique challenges faced by individuals with autism in order to effectively assess and manage their chronic pain.
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[1] Unfortunately, now, in DSM-5, these conditions are lumped together and go under ‘Autism Spectrum Disorder’.
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