Disentangling depression and anxiety in relation to neuroticism, extraversion, suicide, and self-harm among adult psychiatric inpatients with serious mental illness.

OBJECTIVES: Little is known about depression-anxiety comorbidity and its association with personality traits and suicide/self-harm in adult psychiatric inpatients with serious mental illness (SMI), impacting clinical assessment and treatment. This study sought to determine the symptom structure of depression-anxiety comorbidity and its relation to neuroticism, extraversion, and suicide/self-harm behaviour in this high-risk population.

DESIGN: Nine hundred and sixty-two adults receiving inpatient care at a private psychiatric hospital completed questionnaires at admission.

METHODS: Confirmatory factor analyses compared a bifactor solution specifying a general distress factor and two specific depression and anxiety factors against unidimensional and correlated factors solutions. The bifactor solutions' factors were subsequently correlated with neuroticism and extraversion subscales and pre-hospitalization suicide/self-harm behaviours.

RESULTS: The bifactor model rendered superior fit to sample data and a robust general factor - accounting for 77.61% of common item variance - providing the first evidence for a tripartite structure of depression and anxiety among adult inpatients. The bifactor solution-outputted independent general distress, depression, and anxiety factors positively correlated with neuroticism, the personality dimension corresponding to trait negative affectivity. The general distress and depression factors associated with recent self-harm, but factors showed no associations with prior suicidal behaviour.

CONCLUSIONS: In adult psychiatric inpatients, general distress substantially underlies comorbid depression and anxiety symptom variation and may contribute to recent incidence of self-harm. Transdiagnostic assessments and interventions targeting general distress may temper depression, anxiety, and self-harm in adult inpatients.

PRACTITIONER POINTS: Clinical implications Depression-anxiety comorbidity symptomology in adult psychiatric inpatients is primarily composed of general distress. General distress and specific depression are associated with recent self-harm but not suicidal behaviour. Assessing and treating general distress rather than depression or anxiety specifically may best mitigate comorbid depression and anxiety, and reduce self-harm behaviour in this clinical population. Cautions and limitations The large sample lacked ethnocultural diversity, and data were cross-sectional. The use of brief self-report measures to assess depression and anxiety may have reduced measurement range.