Comparison of ImpSS groups on health behaviours at predeployment
| Health behaviours (T1) | Mean (SD) H-ImpSS | Mean (SD) L-ImpSS | t | df | Significance (p) | Effect size (r) |
| Alcohol | ||||||
| Frequency of alcohol | 3.16 (1.3) | 2.73 (1.3) | −5.49 | 1050 | <0.001 | 0.17 |
| Amount of alcohol | 3.97 (2.1) | 3.02 (1.9) | −7.69 | 1035 | <0.001 | 0.23 |
| Frequency of HED (binge) | 2.49 (0.85) | 2.08 (0.96) | −7.179 | 1013 | <0.001 | 0.22 |
| Current perception of intake | 0.16 (1.0) | 0.01 (0.88) | −2.59 | 1030 | <0.01 | 0.08 |
| Smoking | ||||||
| Daily smoking rate | 13.15 (8.7) | 11.27 (8.9) | −2.69 | 649 | <0.01 | 0.11 |
| Current perception of behaviour | 0.24 (0.75) | 0.19 (0.78) | −0.732 | 527 | NS | 0.03 |
| Driving | ||||||
| Speed in built-up area | 1.71 (0.65) | 1.47 (0.58) | −5.87 | 931 | <0.001 | 0.19 |
| Speed on motorway | 2.08 (0.65) | 1.79 (0.65) | −6.96 | 925 | <0.001 | 0.22 |
| Seatbelt use in front as passenger | 0.63 (1.0) | 0.33 (0.78) | −5.47 | 1015 | <0.001 | 0.17 |
| Seatbelt use in rear | 1.43 (1.4) | 1.07 (1.3) | −4.33 | 1069 | <0.001 | 0.13 |
| Sex | ||||||
| Age at first intercourse | 14.9 (1.7) | 15.8 (2.3) | 6.1 | 902 | <0.001 | 0.20 |
| Condom use (for single group only) | 1.96 (1.2) | 1.61 (1.2) | −2.64 | 377 | <0.01 | 0.13 |
| One-night stands | 1.53 (1.2) | 0.80 (1.0) | −10.41 | 1052 | <0.001 | 0.31 |
| Pay for sex | 0.38 (0.74) | 0.22 (0.63) | −3.76 | 1051 | <0.001 | 0.12 |
| Contracted an STI | 0.39 (0.71) | 0.24 (0.59) | −3.87 | 1043 | <0.001 | 0.12 |
| Current perception of behaviour | 0.57 (1.1) | 0.32 (1.0) | −3.95 | 1061 | <0.001 | 0.12 |
| Amount of sex in the last 2 months | 22.3 (24.8) | 18.9 (20.4) | −2.26 | 877 | <0.05 | 0.08 |
HED, Heavy Episodic Drinking; H-ImpSS, high ImpSS; ImpSS, impulsive sensation seeking; L-ImpSS, low ImpSS; STI, Sexually Transmitted Infection.