| in these mental health problems | 11 | other |
| in mood balance | 5 | other |
| to feelings of happiness | 4 | transitive-object |
| serotonin → be → key | 13 |
| serotonin → be → the key | 5 |
| serotonin → be → key player | 5 |
| serotonin → be → factor | 3 |
| serotonin → be → major contributor | 3 |
| serotonin → be → key factor | 3 |
| negative | neutral | positive |
| 0.117 | 0.532 | 0.351 |
| Raw frequency | 32 |
| Normalized frequency | 0.442 |
| Modifier score | 0.500 |
| Perplexity | 77.672 |