Quality of relationships in mothers and their partners in the Avon Longitudinal Study of Parents and Children.

Quality of relationship between partners is associated with a wide range of physical and psychological outcomes like anxiety and depression. There are relatively few longitudinal studies with detailed and repeated measures for quality of relationship, particularly in both partners. The Avon Longitudinal Study of Parents and Children (ALSPAC) is a large birth cohort study in the UK with five post-partum repeated measures of quality of relationship between mothers and their partners assessed using the Intimate Bond Measure (IBM). The Measure includes two subscales named "Care" and "Control". These were measured at 2.75, 6, 9, 12, and 18 years post-partum (baseline N for mothers: 8675; baseline N for partners: 5499). The aims of this data note are to provide a comprehensive overview on the existing IBM data in ALSPAC and to describe both its strengths and limitations for future users. The internal consistency of the subscales were high (Cronbach's alpha 0.95 and 0.88 for the Care and Control subscales) in both mothers and their partners at the baseline. In the Care subscale, all 12 items were highly correlated with the overall score (r>0.62) at the baseline, but in the Control subscale there were three items that had relatively low correlations with the total subscale (r<0.46). This should be taken into account in future research. The longitudinal nature of this data on both mothers and partners will enable detailed explorations of the causes and consequences of differences in quality of relationship.