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This research demonstrates the feasibility of using fine-tuned large language models to estimate depression severity from unstructured user dialogue, effectively addressing data scarcity through pseudo-labeling techniques. By achieving strong clinical metrics without relying on completed self-report questionnaires, the study highlights a viable path toward passive mental health monitoring in AI applications. The work underscores the potential for LLMs to extract continuous symptom records that traditional sparse datasets cannot capture.
Source coveringarXiv

Fine-tuning LLMs for Passive Depression Severity Estimation from AI Mental Health Dialogue

arXiv2 min read

arXiv:2606.17973v2 Announce Type: replace Abstract: Depression is a leading cause of disability worldwide, yet validated questionnaires such as the Patient Health Questionnaire-9 (PHQ-9) often go uncompleted, yielding sparse, biased data. Users of AI mental health applications often describe their mood, sleep and functioning unprompted, producing a continuous record of symptoms. Here, we predict PHQ-9 scores from these conversations alone. As in many clinical language tasks, labels are scarce and imbalanced. We address both by fine-tuning Qwen 3.5 27B with a regression head and augmenting 3,111 ground-truth labels with pseudo-labels from a frontier reasoning model and iteratively trained intermediate models, expanding to 5,524 users with more balanced scores. On 422 held-out users, the model achieved MAE $= 3.98$, Pearson $r = 0.67$, and AUC $= 0.88$ at the clinical threshold (PHQ-9 $\geq 10$); AUC was $> 0.80$ across severity thresholds from PHQ-9 $\geq 3$ to PHQ-9 $\geq 24$, demonstrating that the model captures depression severity across the full clinical spectrum. These results support passive depression monitoring without self-report.

Abstract:Depression is a leading cause of disability worldwide, yet validated questionnaires such as the Patient Health Questionnaire-9 (PHQ-9) often go uncompleted, yielding sparse, biased data. Users of AI mental health applications often describe their mood, sleep and functioning unprompted, producing a continuous record of symptoms. Here, we predict PHQ-9 scores from these conversations alone. As in many clinical language tasks, labels are scarce and imbalanced. We address both by fine-tuning Qwen 3.5 27B with a regression head and augmenting 3,111 ground-truth labels with pseudo-labels from a frontier reasoning model and iteratively trained intermediate models, expanding to 5,524 users with more balanced scores. On 422 held-out users, the model achieved MAE $= 3.98$, Pearson $r = 0.67$, and AUC $= 0.88$ at the clinical threshold (PHQ-9 $\geq 10$); AUC was $> 0.80$ across severity thresholds from PHQ-9 $\geq 3$ to PHQ-9 $\geq 24$, demonstrating that the model captures depression severity across the full clinical spectrum. These results support passive depression monitoring without self-report.

Computation and Language (cs.CL)

arXiv:2606.17973 [cs.CL]

(or arXiv:2606.17973v2 [cs.CL] for this version)

https://doi.org/10.48550/arXiv.2606.17973 Focus to learn more arXiv-issued DOI via DataCite

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Full text under the publisher's open licence · 255 words

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