Self-injury: progress in the understanding of an intractable behavior

Self-injurious behavior (SIB), often arising in the context of stereotyped behavior (SB) is one of the most treatment resistant behavioral disorders in psychiatry. At present, two main hypotheses are prevalent concerning the etiopathogenesis. These deal with abnormalities in central serotonergic functionality or disturbances in the activity of endogenous opioids. Animal and human research reveal some evidence suggesting abnormalities in serotonin functioning, e.g. blunted prolactin and/or cortisol responses to serotonergic challenges and reduced CSF-5-HIAA concentrations in a subgroup of personality disordered males. In addition, treatment with serotonergic agents like SSRIs and the azapirone buspirone demonstrate some beneficial effects on symptoms of aggressive spectrum disorders. Regarding the endogenous opioids, two subhypotheses are well known: addiction and pain. Support for the involvement of endogenous opioids can be derived from animal and human experiments, e.g. the equivocal treatment results with opiate antagonists. Recently, we investigated plasma levels of β-endorphin in a small group of mentally retarded males with long lasting SIB and SB and found a positive correlation between the intensity of SB and plasma levels of β-endorphin. Based on these findings, which are supported by some similar earlier observations, we postulate that β-endorphin can be considered as an indicator of diminished capacity to terminate stress responses. As demonstrated in animal experiments, administration of opiate antagonists in this respect might only be effective in early stages of SIB development.