Indifference or hypersensitivity? Solving the riddle of the pain profile in individuals with autism.

This study tested pain responses in adults with autism versus people without autism. Researchers found that autistic adults actually felt pain more intensely, not less, across different types of heat pain tests. Their pain responses were linked to how severe their autism symptoms were and how sensitive they were to everyday sensations. The study shows that autistic people aren't indifferent to pain as commonly believed - they may actually experience pain more strongly, especially ongoing pain.

This controlled study examined pain processing in 52 adults with autism compared to 52 matched controls using quantitative sensory testing. Contrary to common assumptions about pain indifference in autism, participants with autism showed significantly higher pain ratings across multiple experimental pain tests (single, repetitive, and tonic heat stimuli). The study found that autistic individuals demonstrated hypersensitivity to experimental pain that correlated with daily life pain sensitivity and autism severity. While pain inhibition functioned normally for brief stimuli, it was less efficient for sustained pain - a model that better resembles clinical pain conditions.

These findings support the excitatory-inhibitory imbalance theory in autism and challenge misconceptions about pain indifference.

Healthcare providers should recognize potential pain hypersensitivity in autistic patients rather than assuming indifference. Pain assessment and management strategies may need modification for sustained pain conditions. Caregivers should be aware that autistic individuals may experience heightened sensitivity to painful stimuli.

Study limited to adults with autism; generalizability to children unclear. Laboratory pain testing may not fully reflect real-world pain experiences. Cross-sectional design prevents causal inferences about pain processing mechanisms.

Excitatory-inhibitory (E/I) imbalance is a mechanism that underlies autism spectrum disorder, but it is not systematically tested for pain processing. We hypothesized that the pain modulation profile (PMP) in autistic individuals is characterized by less efficient inhibitory processes together with a facilitative state, indicative of a pronociceptive PMP. Fifty-two adults diagnosed with autism and 52 healthy subjects, age matched and sex matched, underwent quantitative sensory testing to assess the function of the (1) pain facilitatory responses to phasic, repetitive, and tonic heat pain stimuli and (2) pain inhibitory processes of habituation and conditioned pain modulation. Anxiety, pain catastrophizing, sensory, and pain sensitivity were self-reported.

The autistic group reported significantly higher pain ratings of suprathreshold single ( P = 0.001), repetitive (46°C- P = 0.018; 49°C- P = 0.003; 52°C- P < 0.001), and tonic ( P = 0.013) heat stimuli that were cross correlated ( r = 0.48-0.83; P < 0.001) and associated with sensitivity to daily life pain situations ( r = 0.39-0.45; P < 0.005) but not with psychological distress levels. Hypersensitivity to experimental pain was attributed to greater autism severity and sensory hypersensitivity to daily stimuli. Subjects with autism efficiently inhibited phasic but not tonic heat stimuli during conditioned pain modulation. In conclusion, in line with the E/I imbalance mechanism, autism is associated with a pronociceptive PMP expressed by hypersensitivity to daily stimuli and experimental pain and less-efficient inhibition of tonic pain.

The latter is an experimental pain model resembling clinical pain. These results challenge the widely held belief that individuals with autism are indifferent to pain and should raise caregivers' awareness of pain sensitivity in autism.