The missing middle service gap: Obtaining a consensus definition of the 'Missing Middle' in youth mental health

As highlighted in Australia's Productivity Commission Inquiry into mental health, subgroups of individuals are failing to have their needs met, or are 'falling through the cracks' in the current system - a phenomenon increasingly referred to as the 'missing middle'. A barrier to devising solutions is that the term 'missing middle' is not clearly defined. Using the Delphi method, we aimed to define the term and explore acceptability.

Three expert groups were recruited: carers and young people with a lived experience of mental ill-health; clinicians and service providers; researchers, policymakers and commissioners of mental health services. Using a three-stage Delphi process, we elicited definitions, refined and developed a consensus definition.

Ten subthemes describing the 'missing middle' were identified, with four endorsed across all expert groups from the outset: service gap, inflexibility, inadequate service quality and duration, and social disadvantage. Additional subthemes were later endorsed. Feedback was sought on a consensus-driven definition that encompassed the original four endorsed subthemes. Findings supported a shift to a systemic focus - framing the 'missing middle' as a care gap.

A consensus definition was developed, repositioning the term to a systems lens, describing a 'missing middle service gap'. The definition represents the 'missing middle' as a term to describe a gap in care where existing mental health services are not meeting the needs of individuals in a meaningful way. Research was carried out in relation to youth mental health in Australia and the definition may need to be adapted for other contexts.