The therapeutic alliance for adults with intellectual disabilities: a systematic review and measure development study

The therapeutic alliance is a robust predictor of psychological therapy outcomes, yet its conceptualisation and measurement have largely been developed in populations without intellectual disabilities (ID). Consequently, it remains unclear whether existing alliance theory adequately reflects the relational experiences of adults with ID or how the alliance can be meaningfully assessed within ID mental health services. This thesis aimed to examine the therapeutic alliance for adults with ID by evaluating the applicability of Bordin's (1979) alliance model and developing a patient-reported alliance measure informed by these findings.

A qualitative systematic review synthesised evidence from 14 studies using a best-fit framework synthesis to examine mental health professionals' experiences of the therapeutic alliance with adults with ID. Findings indicated that Bordin's dimensions of goals, tasks and bond require conceptual refinement within ID contexts. A secure therapeutic bond emerged as a prerequisite for collaborative goal setting and therapeutic tasks, while systemic influences, including family members, support staff and organisational factors, shaped all aspects of the alliance.

Building on these findings, an exploratory sequential mixed-methods study co-developed a patient-reported therapeutic alliance measure for adults with ID. Candidate items were generated through semi-structured interviews with adults with ID and focus groups with healthcare professionals, analysed using content analysis and reflexive thematic analysis, before refinement through a three-round electronic Delphi study with expert healthcare professionals and consultation with experts-by-experience. The resulting 13-item measure comprises six bond, four tasks and three goals items, reflecting the relative weighting of alliance domains identified across both studies.

Collectively, this thesis reconceptualises the therapeutic alliance in ID contexts as a systemic-relational construct that extends Bordin's original model. It provides a theoretical refinement of alliance conceptualisation and the first co-developed patient-reported alliance measure for adults with ID, establishing a foundation for psychometric evaluation and alliance-informed clinical practice.