| Never smoked | Quit smoking | Light smoker | Heavy smoker | p Value for test of overall differences | |
| Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | Mean (95% CI) | ||
| Easy temperament | 56.7 (55.2 to 58.2) | 57.3 (56.4 to 58.1) | 56.5 (55.8 to 57.1) | 55.7 (55.2 to 56.2) | <0.01 |
| Dimensions of easy temperament | |||||
| Positive mood | 19.2 (18.9 to 19.5) | 19.3 (19.0 to 19.5) | 19.3 (19.0 to 19.5) | 19.0 (18.8 to 19.2) | 0.01 |
| Receptivity to novelty | 20.2 (19.6 to 20.9) | 20.7 (20.3 to 21.1) | 20.1 (19.9 to 21.1) | 20.03 (19.8 to 20.3) | 0.05 |
| Regularity | 17.0 (16.4 to 17.7) | 17.2 (16.9 to 17.5) | 16.9 (16.7 to 17.2) | 16.6 (16.4 to 16.8) | 0.01 |
| Reference | OR (95% CI) | OR (95% CI) | OR (95% CI) | ||
| Difficult temperament | – | 0.82 (0.52 to 1.28) | 0.99 (0.68 to 1.44) | 0.97 (0.60 to 1.58) | |
| Categories of difficult temperament | |||||
| Low positive mood | – | 0.95 (0.81 to 1.10) | 0.96 (0.87 to 1.07) | 1.05 (0.93 to 1.20) | |
| Distress to novelty | – | 0.91 (0.77 to 1.08) | 1.04 (0.97 to 1.11) | 0.97 (0.83 to 1.30) | |
| Irregularity | – | 0.91 (0.68 to 1.23) | 1.10 (0.83 to 1.47) | 1.28 (0.95 to 1.72) |
Differences were statistically significant at *p<0.01, **p<0.001.