Factor mixture modelling of depression and anxiety: Associations with common mental health disorders, service use, and functional impairment

Abstract

Background: Patient-reported outcome measures (PROM) provide clinicians with information about patients’ perceptions of distress. When linked with treatment and diagnostic registers, new information may be obtained, such as associations with prevalence and service use. This study aimed to examine psychological symptoms among psychiatric outpatients and to investigate treatment-relevant characteristics of symptom-homogeneous classes. Methods: In a cohort study of 2473 (63% female) outpatients, factor mixture modelling (FMM) was used to analyse self-reported symptoms of anxiety and depression before treatment, and the classes association with functional impairment, the prevalence of common mental health disorders (CMHD) and the number of assessments and psychotherapy appointments one year after treatment start. Results: Overall, 22% of patients with a CMHD had an additional comorbid mood/anxiety disorder. This comorbid group reported higher symptoms of anxiety and depression compared to patients with non-comorbid anxiety disorders. FMM revealed three classes: “anxiety and somatic depression” (33%), “mixed depression and anxiety” (40%), and “cognitive depression” (27%). The anxiety and somatic depression class was associated with older age, being single and on sick leave, higher probability of depressive-, anxiety-, and comorbid disorders, having more appointments and higher functional impairment. Although the cognitive depression class had less somatic distress than the mixed depression and anxiety class, they reported more functional impairment and had higher service use. Conclusions: The results demonstrate the clinical relevance of applying FMM to PROM data of depression, anxiety, and functional impairment when linked with treatment registers. Three patient groups emerged, with different symptom patterns. Higher symptom severity did not necessarily imply more functional impairment and service use when subdimensions and latent patient groups were accounted for.