Background: Clinical and experimental studies suggest that autistic and schizophrenic patients are insensitive to pain. Stress plays a key role in onset or relapse of symptoms of autism or schizophrenia, but mechanisms are unclear. We studied reactivity to psychosocial, physical and nociceptif stress in patients with autism and early onset schizophrenia (EOS) by assessing behavioural, electrophysiological and neurovegetative responses. Objectives: (1) To study the circadian rhythm of salivary cortisol reflecting hypothalamo-pitiutary axis (HTA) (2) To show a higher response of HTA axis during psychosocial stress procedure and not during a physical stress procedure (cortisol study) (3) Obtain, by RIII reflex assessment, an objective measure of pain perception in autism and EOS, this study should show normal RIII threshold. (4) Showing higher nociceptif inducted vegetative nervous system (VNS) responses in patients with autism and EOS in the same time as lower verbal or emotional reactivity. (5) Showing dissociation between behavioural responses and RIII responses. Methodology: Population: Patients with EOS (n=16), Autism (n=20) and healthy subject (n=22) were compared. Diagnostic was assessed according to DSM IV criteria. Clinical assessments: BPRS, SANS, SAPS, TAS, Coping, STAI, C-GAS, CGI, MADRS, ADI-R and Wechsler scales for EOS patients and ADOS-G and Wechsler scales for Autistic patients. Protocol: Patients with EOS were included for psychosocial stress procedure (P, camera speaking task) and physical stress procedure (B, apartment bicycle riding). P and B procedure were scheduled twice (between 7am and 9am and between 4pm and 6pm) in one day (afternoon session following morning session) or in two days (morning session following afternoon session). During session assessment of cardiac frequency and salivary cortisol sample were collected. Autistic patients and EOS patients (n=10) were included in nociceptif procedure (consisting in progressive electric stimulation in order to raise RIII reflex threshold, capsaicin test to release substance P and EMG for sensitive and motor speed conduction assessment). During this procedure, cardiac and respiratory frequency, psychogalvanic reflex and behavioural reactivity (assessed with PL-BPRS) were measured. Results: EOS patient's cortisol basal profile and circadian rhythm were significatively higher in the morning when compared to healthy subjects. EOS patients starting psychosocial stress procedure in the morning session show an elevated cortisol response in the morning and a lower cortisol response in the afternoon. This difference was not found for healthy subject. All patients (Autism and EOS) had RIII threshold showing no difference when compared to healthy subjects. A sub-group of autistic patients with severe self-injury behaviour show low RIII threshold. We found dissociation between low behavioural reactivity and VNS responses for all patients. This dissociation is particularly notable for cardiac frequency in EOS patients and for respiratory frequency for autistic patients. Discussion: Biological response to stress is more elevated if stress occurs in the morning, linked to psychosocial dimension and novelty. HTA axis may be more solicited in the morning leading to an elevated release of cortisol. Our results suggest that apparent pain insensibility to pain in autism and EOS is more related to cognitive impairments than real endogen analgesia. Preferred responses are from VNS, algic stress couldn't be expressed by verbal or non-verbal behaviour. Psychosocial and nociceptive stress procedure shows in patients (EOS and Autism) higher responses of VNS and HTA axis, particularly in the morning. These results suggest a common dimension between EOS and Autism, particularly about novelty and immuability. These results need further research and are opening therapeutic options.
