The past decade has seen considerable interest in the development and evaluation of complex interventions to improve health. Such interventions can only have a significant impact on health and health care if they are shown to be effective when tested, are capable of being widely implemented and can be normalised into routine practice. To date, there is still a problematic gap between research and implementation. The Normalisation Process Theory (NPT) addresses the factors needed for successful implementation and integration of interventions into routine work (normalisation).

Theories are important tools in the social and natural sciences. The methods by which they are derived are rarely described and discussed. Normalization Process Theory explains how new technologies, ways of acting, and ways of working become routinely embedded in everyday practice, and has applications in the study of implementation processes. This paper describes the process by which it was built.

Background: The Normalization Process Model is a theoretical model that assists in explaining the processes by which complex interventions become routinely embedded in health care practice. It offers a framework for process evaluation and also for comparative studies of complex interventions. It focuses on the factors that promote or inhibit the routine embedding of complex interventions in health care practice. Methods: A formal theory structure is used to define the model, and its internal causal relations and mechanisms. The model is broken down to show that it is consistent and adequate in generating accurate description, systematic explanation, and the production of rational knowledge claims about the workability and integration of complex interventions. Results: The model explains the normalization of complex interventions by reference to four factors demonstrated to promote or inhibit the operationalization and embedding of complex interventions (interactional workability, relational integration, skill-set workability, and contextual integration). Conclusion: The model is consistent and adequate. Repeated calls for theoretically sound process evaluations in randomized controlled trials of complex interventions, and policy-makers who call for a proper understanding of implementation processes, emphasize the value of conceptual tools like the Normalization Process Model.

Objective To gain understanding of general practitioners’ and patients’ opinions of the routine introduction of standardised measures of severity of depression through the UK general practice quality and outcomes framework. Design Semistructured qualitative interview study, with purposive sampling and constant comparative analysis. Participants 34 general practitioners and 24 patients. Setting 38 general practices in three sites in England: Southampton, Liverpool, and Norfolk. Results Patients generally favoured the measures of severity for depression, whereas general practitioners were generally cautious about the validity and utility of such measures and sceptical about the motives behind their introduction. Both general practitioners and patients considered that assessments of severity should be seen as one aspect of holistic care. General practitioners considered their practical wisdom and clinical judgment (“phronesis”) to be more important than objective assessments and were concerned that the assessments reduced the human element of the consultation. Patients were more positive about the questionnaires, seeing them as an efficient and structured supplement to medical judgment and as evidence that general practitioners were taking their problems seriously through a full assessment. General practitioners and patients were aware of the potential for manipulation of indicators: for economic reasons for doctors and for patients to avoid stigma or achieve desired outcomes. Conclusions Despite general practitioners’ caution about measures of severity for depression, these may benefit primary care consultations by increasing patients’ confidence that general practitioners are correct in their diagnosis and are making systematic efforts to assess and manage their mental health problems. Further education of primary care staff may optimise the use and interpretation of depression questionnaires.

Objectives: To determine the acceptability of two psychological interventions for depressed adults in the community and their effect on caseness, symptoms, and subjective function. Design: A pragmatic multicentre randomised controlled trial, stratified by centre. Setting: Nine urban and rural communities in Finland, Republic of Ireland, Norway, Spain, and the United Kingdom. Participants: 452 participants aged 18 to 65, identified through a community survey with depressive or adjustment disorders according to the international classification of diseases, 10th revision or Diagnostic and Statistical Manual of Mental Disorders, fourth edition. Interventions: Six individual sessions of problem solving treatment (n=128), eight group sessions of the course on prevention of depression (n=108), and controls (n=189). Main outcome measures: Completion rates for each intervention, diagnosis of depression, and depressive symptoms and subjective function. Results: 63% of participants assigned to problem solving and 44% assigned to prevention of depression completed their intervention. The proportion of problem solving participants depressed at six months was 17% less than that for controls, giving a number needed to treat of 6; the mean difference in Beck depression inventory score was −2.63 (95% confidence interval −4.95 to −0.32), and there were significant improvements in SF-36 scores. For depression prevention, the difference in proportions of depressed participants was 14% (number needed to treat of 7); the mean difference in Beck depression inventory score was −1.50 (−4.16 to 1.17), and there were significant improvements in SF-36 scores. Such differences were not observed at 12 months. Neither specific diagnosis nor treatment with antidepressants affected outcome. Conclusions: When offered to adults with depressive disorders in the community, problem solving treatment was more acceptable than the course on prevention of depression. Both interventions reduced caseness and improved subjective function.

The Normalization Process Model is a conceptual tool intended to assist in understanding the factors that affect implementation processes in clinical trials and other evaluations of complex interventions. It focuses on the ways that the implementation of complex interventions is shaped by problems of workability and integration.