Low parental tolerance for infant crying: an underlying factor in infant sleep problems?

Parenting behaviours play a major role in the evolution of infant sleep. Sleep problems in infancy have been associated with excessive parental involvement at night-time, and with shorter delays in response to infant night wakings and signalling. Infant crying and sleep problems are linked, yet little is known about the impact of parental responses to crying on infant sleep patterns. This study examined the hypothesis that lower parental tolerance for crying is associated with infant sleep problems. We studied 144 married couples divided into three groups: parents of infants suffering from night-waking problems (i.e. the clinical group), parents of infants without sleep problems and childless couples. Crying tolerance was assessed using questionnaires, audio recordings of crying infants and using a novel paradigm, in which participants were shown a video of a crying infant and asked when they would intervene. Parents in the clinical group demonstrated shorter intervention delays in the crying infant clip (group effect: P < 0.0001), and tended to attribute more distress to the crying infants compared to parents in both control groups (P < 0.05). Additionally, women demonstrated lower tolerance for infant crying on most measures compared to men. Our results suggest that parents of sleep-disturbed infants appear to have lower tolerance for infant crying, which may be a predisposition underlying their excessive involvement in soothing their infants to sleep which may lead to the development of sleep problems. These preliminary findings should be explored further to assess their clinical validity and utility.