Interconnected factors influencing family health and wellbeing in overcrowded homes and points for intervention – A qualitative study in London

• Household overcrowding impacts family health and wellbeing • Multiple factors associated with living in overcrowding —from individual to societal levels—interact to influence outcomes • Targeting these factors and their interactions may improve outcomes for overcrowded families unable to move Household overcrowding contributes to poor familial health/wellbeing and is driven by a shortage of affordable housing. Despite being defined by spatial constraints, the other factors influencing and exacerbating overcrowding's impact remain underexplored. Through focus groups and interviews with London-based professionals working with overcrowded families (n=22) and residents with lived experience (n=25), using thematic analysis we identify aspects of living in overcrowded conditions which affect health/wellbeing outcomes framed according to levels within the Social Ecological Model (SEM). Besides lack of space, overcrowding affects health/wellbeing via a complex web of interactions across personal circumstances, housing suitability/quality, accessibility of amenities/services, and systemic societal challenges. Addressing these factors could improve the lives of families in overcrowded homes, particularly when rehousing may not be feasible in the short term. Household overcrowding contributes to poor familial health/wellbeing and is driven by a shortage of affordable housing. Despite being defined by spatial constraints, the other factors influencing and exacerbating overcrowding's impact remain underexplored. Through focus groups and interviews with London-based professionals working with overcrowded families (n=22) and residents with lived experience (n=25), using thematic analysis we identify aspects of living in overcrowded conditions which affect health/wellbeing outcomes framed according to levels within the Social Ecological Model (SEM). Besides lack of space, overcrowding affects health/wellbeing via a complex web of interactions across personal circumstances, housing suitability/quality, accessibility of amenities/services, and systemic societal challenges. Addressing these factors could improve the lives of families in overcrowded homes, particularly when rehousing may not be feasible in the short term.