Background: Our previous research demonstrated that mild depression (MD) is characterized by patterns of atypical language use such as inverted word order, greater repetition, increased use of reflexive/personal (e.g. myself) or negative/ indefinite (e.g. nobody) pronouns, verbs in past tense, and other lexico-grammatical, stylistic and syntactic indicators (how the patient speaks). We now investigate the role of semantic features (what the patient speaks about) in diagnosing (why it is important to listen) affective states.
Subjects and methods: 201 written narratives from 124 patients with MD and 77 healthy controls (HC), including 35 cases of normal sadness (NS), were studied using principle component lexis analysis. Statistical data evaluation was performed with SPSS-25 (p<0.05, significant) and included the Cohen's kappa for inter-rater reliability, nonparametric methods to measure between-group differences (Mann-Whitney U-test, Pearson Chi-square test, Kruskal-Wallis, one-way ANOVA), and discriminant analysis for modeling of semantic variables related to affective diagnostic types.
Results: Component lexis analysis revealed an exaggerated usage of semantic categories describing existential and family values in the texts of MD patients compared to HC. However, there were fewer cognitive and altruistic categories presented in patients' self-reports. The most substantial between-group difference was the lesser semantics of self-realization in MD patients, as well as their significantly lower ranking of social status' priorities. Communicative and hedonic values in MD speech displaced and predominated in ranking over the values of social status, versus the opposite relationship in HC speech. The discriminant model revealed a set of semantic indicators significantly distinguishing the MD, HC and NS groups (96.3%; Wilks' λ=0.001, p<0.001, r=0.996).
Conclusions: Linguistic structure and content of patients' verbalizations may serve as diagnostic markers of MD. Evaluation of psychosocial themes within the content of narratives should enable a better understanding of MD pathogenesis and emphasize the importance of monitoring social difficulties during treatment.