---
title: BPSD — Depression
type: concept
last_updated: 2026-04-25
sources:
  - code/kb_loader/data/clinical/bpsd/depression.json
status: settled
---

# Depression

Common in MCI and early AD; may pre-date or accelerate cognitive decline.

## Sensor signature

- **Activity:** reduced (psychomotor retardation)
- **HRV:** reduced (autonomic dysregulation overlaps with AD pattern — confound)
- **Voice:** flat prosody, reduced speech rate, longer pauses
- **Sleep (PPG+IMU):** disrupted, often early-morning awakening

## Distinguishing from apathy

Depression = persistent low mood + psychomotor signs + sleep disturbance. Apathy = motivation deficit without low mood. Voice and self-report content discriminate; the [Language-cognitive agent](../agents/language_cognitive_agent.md) tracks linguistic markers of mood.

## Intervention

Behavioural activation prompts; clinical referral if persistent. See [Intervention agent](../agents/intervention_agent.md).

KB: [`code/kb_loader/data/clinical/bpsd/depression.json`](../../code/kb_loader/data/clinical/bpsd/depression.json). Umbrella: [BPSD](bpsd.md).