Intranasal oxytocin administration improves mood in new mothers with moderate low mood but not in mothers with elevated symptoms of postnatal depression: A randomised controlled trial

Background: Oxytocin (OT) is a neuropeptide hormone that has anxiolytic and antidepressant effects, and positive effects on social affiliation and behaviour, particularly in parenting and attachment relationships. In women with postnatal depression (PND), each of these are reduced. This study investigated if OT administration reduces low mood in new mothers with PND and across the low mood spectrum. Design: A double-blind, placebo-controlled, randomised controlled-trial, within-subjects, cross-over design was conducted. Participants: Mothers (N = 58) between 3 and 9 months postpartum. Participants were screened for traits of PND on the Edinburgh Postnatal Depression Scale (EPDS) and assigned into 2 groups: probable PND cases (N = 26, scoring ≥9) and controls (N = 32, scoring ≤9). Method: Participants rated their current mood on the Positive and Negative Affect Scale (PANAS) at Baseline (before nasal administration), Condition 1 (after first OT/Placebo administration) and Condition 2 (after second OT/Placebo administration). Results: OT administration did not affect mood in women with PND scores above the cut-off point but significantly reduced negative mood in those scoring below the cut-off point. To explore if a subgroup was driving this, we compared participants with mild, moderate and severe scores on the EPDS. OT administration significantly reduced negative mood in women with moderate low mood scores on the EPDS. Limitations: PND was assessed by the EPDS, rather than a clinical diagnosis. Conclusion: These results illustrate individual differences in response to OT administration and suggest that OT administration may offer treatment benefit to new mothers who report moderate sub-clinical levels of depression.