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Plasma beta-endorphin concentrations in people with learning disability and self-injurious and/or autistic behaviour
S H Willemsen-Swinkels1, J K Buitelaar, F G Weijnen
1Rudolf Magnus Institute for Neurosciences, Department of Child and Adolescent Psychiatry, Utrecht University, The Netherlands.
Background:
It has been suggested that the key variable in reduced plasma immunoreactive beta-endorphin concentrations in autistic subjects may be concomitant self-injurious behaviour.
Method:
We studied morning levels of plasma beta-endorphin in 33 learning disabled people with self-injurious and/or autistic behaviour.
Results:
The beta-endorphin level of the subjects with severe self-injurious behaviour proved to be significantly lower than of autistic subjects without severe self-injurious behaviour (3.6 (1.4) pmol/l v. 5.8 (4.3) pmol/l; t-test: P = 0.045. Replication: 3.7 (1.1) pmol/l v. 5.7 (3.8) pmol/l; t-test: P = 0.043). Individuals with mild and occasional self-injurious behaviour were found to have beta-endorphin levels comparable to those without self-injurious behaviour. Further, subjects being treated with neuroleptics and lower beta-endorphin levels than untreated subjects.
Conclusions:
These results stress that in any study of opioid systems of learning disabled people, it is very important to differentiate between people with and without severe self-injurious behaviour. The results support the idea that severe self-injurious behaviour may be related to functional disturbances in the endogenous opioid system.