| for several hours | 8 | temporal |
| in some cases | 4 | temporal |
| either longer | 4 | temporal |
| symptom → can → last | 22 |
| symptom → be → prolonged | 14 |
| symptom → be → lasting | 5 |
| symptom → be → long-lasting | 4 |
| symptom → become → prolonged | 3 |
| negative | neutral | positive |
| 0.579 | 0.381 | 0.040 |
| Raw frequency | 48 |
| Normalized frequency | 0.504 |
| Modifier score | 0.850 |
| Perplexity | 78.602 |