Clinical and cost-effectiveness of parenting intervention for mothers experiencing psychosocial stress: insights from the early closure of the Mellow Babies RCT
Authors: Thompson Lucy , Tanner Jessica , Breckons Matthew , Young Naomi , Ternent Laura , Vadiveloo Thenmalar , Wilson Philip , Wight Danny , Marryat Louise , McGowan Iain , MacLennan Graeme , MacBeth Angus , McTaggart James , Allison Tim , Norrie John 
Published: December 2024

Background
Problems in children’s early social and emotional development are likely to have major long-term consequences for the individual and society: maternal emotional well-being is associated with better outcomes. Interventions designed to improve both maternal mental health and the mother–child relationship are thus likely to benefit both maternal health and child development.

Objectives
To establish the clinical and cost-effectiveness of the Mellow Babies parenting intervention for women experiencing psychosocial stress and their 6- to 18-month-old babies. Secondary aims included understanding the process of recruitment, retention and engagement in both the trial and the intervention.

Design
This was a single-centre randomised controlled trial, employing 1 : 1 randomisation with participants allocated to receive Mellow Babies plus usual care, or usual care only.

Setting
Community settings in the Highland Council region of Scotland.

Participants
We aimed to recruit 212 mothers to provide evaluable data for 170 participants (90% power to detect an effect size of 0.5 for the primary outcome). Eligible mothers lived within the Highland Council region; were aged ≥ 16 years; had primary caregiving responsibility of a baby aged 6–18 months and scored above threshold for anxiety (≥ 11) and/or depression (≥ 7) on the Hospital Anxiety and Depression Scale.

Intervention
Mellow Babies is a 14-week group-based parenting programme specifically designed for mothers with psychosocial difficulties. Sessions run for 5 hours each and include 4–10 participants.

Main outcome measures
Maternal Hospital Anxiety and Depression Scale scores at 8 months post randomisation and when the child reaches 30 months. Health economic (service use and quality of life) and child development (language development and mental well-being) outcomes were also examined.

Results
Due to the COVID-19 pandemic, the trial did not recruit to target: 106 women were recruited (53 per arm). It was not possible to explore the clinical and cost-effectiveness of Mellow Babies. Baseline, follow-up and process evaluation data were analysed to allow optimal learning from the study. Direct communication (letter) combined with health visitor referral was a better means of recruitment. Despite relatively low sociodemographic disadvantage, there was a high prevalence of mental ill health. Retention to follow-up and within the intervention was good (75% to study end point), and data were well-completed. Quality-of-life ratings increased at 8 months post randomisation, then decreased somewhat at 30 months of age, but remained above baseline. Qualitative interviews highlighted barriers and facilitators of engagement with the intervention groups. There was no observed difference in baseline characteristics or outcomes between participants recruited before and after the pandemic, although the logistical impact on the trial was profound.

Limitations
The study was not sufficiently powered to answer the main outcome questions. The occurrence of the COVID-19 pandemic severely hampered the current trial.

Conclusions
This trial was not able to answer questions on clinical and cost-effectiveness. Learning from this trial could inform a new re-designed trial including cluster randomisation and based within a larger and more varied population.

Future work
There is still a need for a definitive trial of Mellow Babies. It would likely be most fruitful to conduct a cluster randomised trial, with full buy-in from key health service stakeholders and front-line practitioners, to maximise recruitment, engagement and participation.

Trial registration
The trial is registered as ISRCTN47575326.

Funding
This award was funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme (NIHR award ref: 15/126/05) and is published in full in Public Health Research; Vol. 12, No. 17. See the NIHR Funding and Awards website for further award information.