Japanese infants' attachment insecurity and externalizing/internalizing problems: Using strange situation and attachment Q-sort methods.

According to attachment theory, an infant-mother attachment is universal, and infants who develop an insecure attachment relationship with their mother are likely to show mental health problems compared to those who develop a secure attachment relationship. These hypotheses have been empirically supported in Western cultures. However, the cross-cultural evidence is still insufficient. The purpose of this study was to examine the association between Japanese infants' attachment insecurity and mental health problems. We studied 81 Japanese infants (M age = 14.64 months, SD = 1.43, females = 54%) mostly from middle-class families. The Strange Situation Procedure (SSP) and Attachment Q-sort (AQS) assessed infant attachment security. Infant externalizing and internalizing problems were rated concurrently by the mother and 6 months later by the mother and another adult (father or grandmother). Japanese infants' attachment insecurity measured by the AQS was associated with their externalizing problems concurrently and 6 months later. Infants with insecure-resistant attachment measured by the SSP had higher externalizing problems compared to those with secure attachment concurrently (not 6 months later). Attachment insecurity was not related to internalizing problems. These findings partly supported the association between attachment insecurity and mental health problems. This research also recommends observing infant attachment at home.