Objectives: Credible evaluations of the psychological treatment of morbid jealousy are rare. The aim of this study was to evaluate temporal responsivity to cognitive behavioural therapy (CBT) and cognitive analytic therapy (CAT) for morbid jealousy.

Design: The methodology involved matched A/B single-case experimental designs (SCED) with extended follow-up, in which two patients and their partners completed daily jealousy target symptom items across the phases of the study. Patients also completed traditional psychometric outcome measures at assessment, post-therapy, and at final follow-up.

Methods: Both patients received the same number of assessment (n = 3), treatment (n = 13), and follow-up (n = 1) sessions.

Results: Autoregressive Integrated Moving Average (ARIMA) models of the patients' daily target symptom jealousy SCED data indicate the effectiveness of the CAT intervention and the ineffectiveness of the CBT intervention, but both therapies produced large effect sizes. The partner of the CBT patient felt less controlled following therapy, whilst the partner of CAT patient did not perceive any change to his partner.

Conclusion: The discussion calls for a stronger evidence base for the psychological treatment of morbid jealousy to be constructed and debates the routine measurement of outcomes for partners of morbidly jealous patients.

Practitioner points: Measuring outcomes for partners of jealous patients is indicated. CAT shows promise as an intervention for morbid jealousy. The evidence base for the treatment of morbid jealousy requires further development.