“The effects of an internet-based intervention (“Mamma Mia”) on perinatal anxiety: Secondary findings from a randomized trial”

• Women who used Mamma Mia showed a small but significant decrease in anxiety symptoms compared to the control group. • Women with higher anxiety levels at baseline experienced a greater effect of reduced anxiety with exposure to the intervention. The intervention was more effective in reducing anxiety among women who reported higher levels of anxiety at baseline. • Over time, women in the Mamma Mia group consistently showed a low probability of reaching clinical levels of anxiety, which may indicate a preventive effect of the intervention. • Although individual symptom reduction was small, the study suggests that universal digital interventions may have a significant preventive effect at the population level. Mamma Mia is a universal internet-based self-help intervention developed to promote perinatal mental health by addressing risk and protective factors specific to the perinatal phase. Previous research has shown its effectiveness in reducing perinatal depressive symptoms. Given that perinatal anxiety often coexists with depression and affects 20–25% of women, early intervention is essential. This study examined the effectiveness of Mamma Mia in reducing perinatal anxiety symptoms. Specifically, we assessed whether (1) anxiety symptoms were lower in the intervention group, (2) the effect changed over time, and (3) baseline anxiety moderated outcomes. Finally, we examined if the prevalence of mothers with possible anxiety differed between the intervention and control groups. A randomized controlled trial included 1,332 pregnant women assigned to Mamma Mia or a control group. Data were collected at gestational weeks 21–25 and 37, as well as 6 weeks, 3 months, 6 months, and 12 months postpartum. Anxiety symptoms were measured using the anxiety subscale of Edinburgh Postnatal Depression Scale (EPDS–3A), with an EPDS–3A score ≥ 5 indicating possible anxiety. Data were analyzed using linear mixed-effects models. Participants in the Mamma Mia group reported fewer anxiety symptoms than the control group across all time points ( p < .001). The group-by-time interaction was not significant, consistent with the difference between groups remaining stable over time. However, the effect was greater for those with higher baseline anxiety, and the prevalence of EPDS–3A scores ≥ 5 was consistently lower in the intervention group. Mamma Mia shows promise as an effective intervention for reducing perinatal anxiety.