Altered diurnal pattern of salivary substance P in adults with developmental disabilities and chronic self-injury

Morning and afternoon salivary substance P and cortisol levels were measured in 26 adults with chronic self-injurious behavior (SIB) and severe developmental disabilities and compared with matched controls without SIB. Chronic SIB was associated with an altered diurnal pattern of salivary substance P relative to matched controls, characterized primarily by lower levels of morning substance P, which were significantly correlated with overall severity of SIB. There was a trend for SIB subjects to exhibit higher levels of cortisol, which was significantly correlated with overall severity of SIB. These results support a model of altered nociception and possible stress-induced analgesia among individuals with developmental disability and chronic SIB.