Publication date: January 2014Source:Peptides, Volume 51 Author(s): Lennart Righard , Anna Carlsson-Jonsson , Fred Nyberg An incorrect, superficial suckling technique in breastfeeding frequently leads to milk congestion and sometimes mastitis. In the present study we have examined whether milk congestion may affect levels of the atypical opioid β-casomorphin-8 in milk and in plasma. We also investigated whether the rate of acute psychosis during the first half year after parturition has declined in Sweden over the years. Milk and plasma samples were collected for peptide analysis from 14 women with mastitis and 10 controls. We found that in a group of 14 late cases of mastitis (median 48 days post partum) the detected mean level of β-casomorphin-8 in milk was significantly higher and somewhat higher in plasma at the acute stage compared with 2–3 weeks later, after recovery when the symptoms had disappeared, as well as compared to the control subjects. Swedish official statistics show that the incidence of acute psychosis in the first month and in the first half year after birth has declined by a half during the last 30 years. A relationship between postpartum psychosis and elevated β-casomorphin-8 levels in CSF has been suggested from earlier studies. In this study, milk congestion led to enhanced levels of β-casomorphin-8 in milk, which may be related to postpartum psychosis and probably also to ‘the postnatal blues’.