This study investigates the effects of a single dose of oxytocin (OT) delivered via a nasal spray in women with and without traits of postnatal depression (PND).

A double-blind, placebo-controlled, case-controlled, randomised controlled-trial, within-subjects, cross-over design will be conducted.

Participants will include mothers and their infant in the postnatal period. All participants will be screened for symptoms of low mood on the Edinburgh Postnatal Depression Scale (EPDS) and then assigned into 2 groups comprising probable PND cases and controls.

All participants will take part in 3 conditions at Baseline (before nasal spray administration), Condition 1 (after first OT/Placebo administration) and Condition 2 (after second OT/Placebo administration), and will complete the same order of tasks.

Inclusion Criteria:

• All mothers will be aged ≥18 years old.
• Mothers in the clinical group will score above the clinical cut-off point on the EPDS.
• Mothers in the control group will score below the clinical cut-off point on the EPDS.
• Mothers must be able to read and write English at a level sufficient to complete study related assessments.

Exclusion Criteria:

• If the mother is younger than 18 or post-menopausal
• If the pregnancy was a result of fertility treatment
• If the mother is pregnant
• If the mother has history of psychotic illness
• If the mother is at risk of self-harm
• If the mother is involved in other active drug trials