# Association of oral health related subjective quality of life and severity of negative symptoms of treatment-resistant schizophrenia: a cross-sectional study in Croatia

## TL;DR

Poor oral health is strongly linked to severe negative symptoms in treatment-resistant schizophrenia patients in Croatia.

## Contribution

This study identifies a significant association between oral health-related quality of life and negative symptoms in treatment-resistant schizophrenia.

## Key findings

- Total SNS scores were significantly associated with OHR-sQoL scores after adjusting for covariates.
- Diminished emotional range and anhedonia were specifically linked to oral health functional limitations.
- The association remained robust even after controlling for multiple variables.

## Abstract

Patients diagnosed with schizophrenia, particularly those with severe negative symptoms (NS) and treatment resistant schizophrenia (TRS), have poorer oral health than the general population, which can have serious consequences beyond oral and dental problems, but remains poorly addressed in psychiatric clinical practice and mental health research.

To investigate the association between oral health-related subjective quality of life (OHR-sQoL) and severity of NS in TRS.

We conducted a cross-sectional study in a tertiary psychiatric clinic in Croatia during 2022-2023. The target population were patients diagnosed with TRS with more pronounced NS. The outcome was the Self-Evaluation of Negative Symptoms (SNS) scale and its five dimensions. Exposure was OHR-sQoL measured by the Oral Health Impact Profile questionnaire (OHR-sQoL). We tested the hypothesis using multivariable linear hierarchical regression analysis.

We enrolled 130 participants with a median (interquartile range) age of 43 (36-51) years, with an equal number of women and men. Total SNS and OHR-sQoL scores were found to be significantly associated in both bivariate and multivariable analysis adjusted for a large number of covariates (R2 increase over the effect of covariates = 0.22; p < 0.001; false discovery rate < 5%). Total SNS score was significantly associated with the functional limitation dimension of the OHIP-49, as well as diminished emotional range with psychological discomfort, physical and psychological disability, and anhedonia with functional limitation.

Figure 1. Scatter plot of the correlation between the total score of the Self-evaluation of Negative Symptoms (SNS) and the Oral Health Impact Profile (OHIP-49); the solid line represents the 80% smoothed local polynomial regression curve; the dashed line represents the linear regression line (n = 130)

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NS of TRS are relatively strongly associated with OHR-sQoL, especially with functional limitations. The robustness of this association was confirmed by controlling for a large number of covariates. If the relationship between NS and OHR-sQoL is bidirectional, which should be verified by future studies, perhaps for further progress in solving the serious problems of NS and TRS it will be necessary to include the comorbidity with oral diseases and oral functional disorders and OHR-sQoL.

None Declared