eTable 1. Sample characteristics at baseline. Tests for differences between IG und CAU/WL (χ² tests for items with nominal scale. t tests for items with interval scale).
| Variable | IG (n. %) (N = 306) |
CAU/WL (n. %) (N = 302) |
χ ² test (df. χ² value) | Significance (p value) |
| Sex | Male = 136 (44%) Female = 170 (56%) |
Male = 153 (51%) Female = 149 (49%) |
χ²(1) = 2.235 | 0.135 |
| Highest school education | General higher Education Entrance Qualification (Abitur) = 116 (41.4%) Secondary school certificate (Realschule) = 164 (53.6%) Other = 26 (5%) |
General higher Education Entrance Qualification (Abitur) = 142 (49.5%) Secondary school certificate (Realschule) = 144 (47.7%) Other = 16 (2.8%) |
χ²(1) = 3.703 | 0.054 |
| Job qualification | Apprenticeship = 203 (66.3%) Academic Studies = 78 (25.5%) No qualification = 17 (5.6%) Other = 8 (2.6%) |
Apprenticeship = 185 (61.3%) Academic Studies = 97 (32.1%) No qualification = 18 (6.0%) Other = 2 (0.7%) |
χ²(3) = 6.5 | 0.09 |
| Job status | Working*1 = 236 (77.1%) Learning*2 = 15 (4.9%) Not working = 45 (14.7%) Other = 10 (3.3%) |
Working = 239 (79.1%) Learning = 20 (6.6%) Not working = 41 (13.6%) Other = 2 (0.7%) |
χ²(2) = 0.892 | 0.64 |
| Relationship status | Relationship yes = 128 (41.8%) Relationship no = 178 (58.2%) |
Relationship yes = 132 (43.7%) Relationship no = 170 (56.3%) |
χ²(1) = 0.187 | 0.665 |
| Children (at least 1) | Children yes = 92 (30.1%) Children no = 214 (69.9%) |
Children yes = 95 (31.5%) Children no = 207 (68.5%) |
χ²(1) = 0.119 | 0.73 |
| Use of help system because of alcohol consumption | Treatment yes*3 = 39 (12.8%) Treatment no*3 = 267 (87.2%) |
Treatment yes = 51 (16.9%) Treatment no = 251 (83.1%) |
χ²(1) = 2.068 | 0.15 |
| Variable | IG (M. SD) | CAU/WL (M. SD) | t test (df. t value) | Significance (p value) |
| Age | 40.4 (11.2) | 40.7 (12.1) | t(607) = 0.410 | 0.682 |
| Age—first time drinking of an alcoholic beverage | 15.04 (3.23) | 14.94 (2.13) | t(607) = 0.475 | 0.635 |
| Age—starting regular alcohol consumption (min. 1 time per month) | 17.50 (4.21) | 17.51 (4.05) | t(607) = 0.005 | 0.996 |
| Primary outcomes | ||||
| QFI (amount of alcohol in gram over the past 30 days) | 63.69 (61.84) | 61.64 (58.84) | t(606) = −0.348 | 0.728 |
| TFB (amount of alcohol in gram over the past 7 days) | 52.91 (56.68) | 46.82 (41.18) | t(606) = −1.514 | 0.131 |
| Secondary outcomes | ||||
| Days of Binge Drinking within the past 30 days | 16.79 (11.45) | 15.27 (11.72) | t(599) = −1.605 | 0.109 |
| Days of drunkenness within the past 30 days | 4.42 (5.15) | 4.09 (4.67) | t(599) = −0.831 | 0.406 |
*1 Working—in job. apprenticeship or traineeship
*2 Learning—students in the university or school
*3 Treatment includes: general practitioner. psychiatrist/neurologist. psychologist/psychotherapist. other medical specialists. traditional healer. self-help group. hospital detoxification. hospital rehabilitation. ambulant drug addiction counseling. support by friends/partner/family. other
CAU/WL. care as usual/waiting list; df. degrees of freedom; IG. intervention group; M. mean; QFI. Quantity-Frequency Index; SD. standard deviation; TFB. Timeline Follow-Back method