Abstract
Parenthood contributes to lasting changes in brain structure, function, and cognition, with emerging evidence suggesting a neuroprotective effect against cognitive ageing. Long-term environmental complexity is a recognised contributor to cognitive reserve. We recently proposed that the enduring cognitive and emotional demands of parenthood represent a unique form of environmental complexity. However, the absence of a well-defined construct capturing lifetime engagement in parenthood limits our ability to examine its impact on the parental brain. This qualitative phase of a mixed methods study examines how parents conceptualise the cognitive demands of caregiving across the lifespan, providing a conceptual foundation for the Lifetime Engagement in the Activities of Parenthood (LEAP) scale. Twenty-nine parents (21 mothers, 8 fathers) participated in one of five focus groups exploring the psychological and environmental demands of parenthood. Data were analysed using reflexive thematic analysis within a critical realist framework. Three themes were developed: thinking work, feeling work, and personal transformation, each enduring and evolving from the peripartum period into late life. Taken together, these findings position lifelong engagement in parenthood as a form of environmental complexity that may influence normative ageing and contribute to cognitive reserve in late life.