Can patients diagnosed with schizophrenia complete choice-based conjoint analysis tasks?

Background: Schizophrenia is a severe mental illness associated with hallucinations, delusions, apathy, poor social functioning, and impaired cognition. Researchers and funders have been hesitant to focus efforts on treatment preferences of patients with schizophrenia because of the perceived cognitive burden that research methods, such as conjoint analysis, place on them.

Objective: The objective of this study was to test if patients diagnosed with schizophrenia were able to complete a choice-based conjoint analysis (often referred to as discrete-choice experiments) and to test if meaningful trade-offs were being made.

Methods: German outpatients diagnosed with schizophrenia were eligible to participate in this study if they were aged 18-65 years, had received treatment for at least 1 year and were not experiencing acute symptoms. Conjoint analysis tasks were based on six attributes, each with two levels, which were identified via a literature review and focus groups. A psychologist in a professional interview facility presented each respondent with the eight tasks with little explanation. All interviews were recorded, transcribed, and analyzed to verify that respondents understood the tasks. Preferences were assessed using logistic regression, with a correction for clustering.

Results: We found evidence that the 21 patients diagnosed with schizophrenia participating in the study could complete conjoint analysis tasks in a meaningful way. Patients not only related to the scenarios presented in conjoint tasks, but explicitly stated that they used their own preferences to judge which scenarios were better. Statistical analysis confirmed all hypotheses about the attributes (i.e. all attributes had the expected sign). Having a supportive physician, not feeling slowed, and improvements in stressful situations (p < 0.01) were the most important attributes.

Conclusions: We found that patients diagnosed with schizophrenia can complete conjoint analysis tasks, that they base their decisions on their own preferences, and that patients make trade-offs between attributes.