RESUMEN
RATIONALE, AIMS AND OBJECTIVES: The concept of patient or case complexity is relevant-and widely used-at all levels and stages of mental health service provision, but there have been few methodologically robust attempts to define this term. This study aimed to establish a consensus on factors contributing to patient complexity in adult psychological services using Delphi methodology. METHOD: Applied psychologists in a single urban/suburban UK National Health Service setting took part in a three-round modified Delphi study. Twenty-eight respondents in Round 1 gave qualitative data on factors they considered when assessing complexity, which was subject to thematic analysis. Twenty-five respondents in Round 2 rated how central/peripheral each theme was to their judgement using Likert scales. In a third round, 20 respondents addressed discrepancies and possible utilities of the emerging framework. RESULTS: Thirteen factors contributing to patient/case complexity (active severe/enduring mental health, current coping/functioning, engagement, forensic history, iatrogenic factors, interpersonal functioning, neurocognitive functioning, physical health, problematic substance use, risk, severity/chronicity of presenting problems, systemic and socioeconomic factors and trauma) were identified with a high degree of consensus. All were rated as central to complexity. CONCLUSIONS: We conclude that applied psychologists do have a shared understanding of complexity and make recommendations for further research validating, developing and applying this empirically derived framework.