Psychiatric Symptom Profiles Predict Functional Impairment

Abstract

Objective: Mental illness often interferes with daily functioning and an individual's pattern of psychiatric signs and symptoms may predict risk of future disability. Understanding the linkage between psychiatric symptoms and impaired functioning is critical for accurate rehabilitation planning and legal assessment. Here, we investigated the stability of functional impairment measures over 18 months and their association with psychiatric symptoms. Moreover, we developed a clinical self-report measure that allows estimation of functional impairment levels over 18 month observation periods. Methods: Consecutively treated outpatients and daycare patients (N = 155) from several psychiatric units in Switzerland completed the Dissociative Experiences Scale, Somatoform Dissociation Questionnaire, Multidimensional Inventory for Dissociation, Beck Depression Inventory, Brief Symptom Inventory, and WHO Disability Assessment Schedule at baseline, 6, 12, and 18 month follow-up examinations. The association between symptoms functional impairment over time was investigated using longitudinal linear mixed models. Penalized regression was used to identify questionnaire items that best predicted functional impairment. Results: We found high stability in the extent of functional impairment over 18 months. Fear of negative evaluation, fatigue, concentration problems, negative alterations in mood, and dissociative symptoms showed the strongest association with functional impairment measures. The empirically derived scale for functional impairment prediction explained between 0.62 and 0.77 of the variance in disability across various life domains. Conclusion: Given the capability for somatic and mental symptoms associated with social anxiety, depression, and dissociation to predict future disability, these symptoms have strong potential for guiding rehabilitation planning and prognostic evaluation in insurance medicine. The Functional Impairment Prediction Scale may serve as a valuable, empirical-based extension in legal assessments of how work capacity is affected by psychological factors.

Keywords: daily functioning; disability; functional impairment; insurance medicine; legal assessment; occupational health.

Figure 1

Functional impairment across WHODAS II domains during 18 months in outpatients and day-care patients (N = 155) by DSM-IV diagnostic category. The thick red line represents the mean functional impairment score and the associated ribbon the standard deviation. The colored thin lines represent functional impairment scores of individual cases. Higher scores represent higher impairment across life domains.

Figure 2

Symptom severity during 18 months in outpatients and daycare patients (N = 155) by DSM-IV diagnostic category. The thick red line represents the mean score across symptoms belonging to this diagnostic category and the associated ribbon the standard deviation. The colored thin lines represent the mean score across subjects of each symptom belonging to this diagnostic category. Higher scores represent higher severity.

Figure 3

Association between DSM-5 symptoms and functional impairment across WHODAS II domains during 18 months in outpatients and daycare patients (N = 155). The order of the symptoms in the graph represent descending magnitudes of the mean standardized parameter estimate across the symptoms related to a diagnosis, followed by the standardized parameter estimate magnitude of each symptom related to a diagnosis. The DSM-5 symptom criterion for a symptom is given in parenthesis.