Table 1.
Comparison of baseline characteristics of included and excluded participants.
| Included (n=946) | Excluded (n=307) | |||
|---|---|---|---|---|
| % (n) | Mean (SD) | % (n) | Mean (SD) | |
| Sex (% male) | 46.0 (435) | 56.4 (173)* | ||
| Race (% White) | 71.2 (674) | 68.7 (211) | ||
| Alcohol use characteristics a | ||||
| DSM-IV Status b | ||||
| Dependence | 16.1 (140) | 15.3 (42) | ||
| Abuse | 12.2 (106) | 16.1 (44) | ||
| Diagnostic orphan c | 40.5 (351) | 39.1 (107) | ||
| Non-problematic | 31.1 (270) | 29.6 (81) | ||
| Typical number of drinks/drinking day | 4.8 (2.6) | 5.2 (3.0)* | ||
| Past-year frequency of drinking | 50.8 (48.1) | 58.3 (54.7)* | ||
| Age first drank alcohol | 14.7 (2.3) | 14.6 (2.5) | ||
| Marijuana use characteristics d | ||||
| DSM-IV Status b | ||||
| Dependence | 9.2 (53) | 12.6 (22) | ||
| Abuse | 15.6 (90) | 9.2 (16) | ||
| Diagnostic orphan c | 12.5 (72) | 15.5 (27) | ||
| Non-problematic | 62.8 (363) | 62.6 (109) | ||
| Past-year frequency of use | 35.2 (64.2) | 47.5 (81.1)* | ||
| Age first used marijuana | 16.0 (1.5) | 15.9 (1.7) | ||
Denotes statistically significant difference between participants and non-participants (p<.05). Mean differences in alcohol frequency, alcohol quantity, and marijuana frequency became non-significant when sex was held constant.
Results based on 867 included and 288 excluded participants who were past-year alcohol users at baseline.
In the “excluded” column, cell counts for DSM-IV status do not sum to column totals due to missing data on individual DSM-IV items.
“Diagnostic orphan” refers to individuals endorsing 1 or 2 dependence criteria but not meeting the definition for abuse or dependence.
Results based on 578 included and 201 excluded participants who were past-year marijuana users at baseline.