Table 1. Demographic and baseline variables for adolescents and adults.
| Adolescents (n=20) | Adults (n=20) | Test statistic | P-value | |
|---|---|---|---|---|
| Mean (s.d.) | Mean (s.d.) | |||
| Demographics | ||||
| Age (years) | 17.08 (0.44) | 25.49 (1.07) | U=400.000 | <0.001* |
| Body weight (kg) | 66.40 (10.30) | 74.96 (10.12) | U=296.000 | 0.009* |
| Cannabis weight (mg) | 58.90 (7.65) | 65.44 (6.56) | U=299.500 | 0.006* |
| Verbal IQ (n=39) | 110.20 (11.29) | 115.11 (8.70) | U=245.000 | 0.127 |
| Baseline questionnaires | ||||
| Beck Anxiety Inventory | 4.55 (4.62) | 6.45 (7.09) | U=234.500 | 0.355 |
| Beck Depression Inventory | 6.35 (4.66) | 4.55 (4.38) | U=152.000 | 0.201 |
| SUPPS-P Impulsive Behaviour Scale | 45.55 (8.00) | 45.40 (5.94) | t38=0.067 | 0.947 |
| Schizotypal Personality Questionnaire | 20.90 (10.90) | 15.21 (11.24) | U=145.000 | 0.142 |
| Cannabis use | ||||
| Age first tried cannabis (years) | 14.73 (1.25) | 17.71 (3.00) | U=338.000 | <0.001* |
| Last used cannabis (days) | 3.35 (2.52) | 4.75 (3.78) | U=259.500 | 0.108 |
| Duration of cannabis use (years) | 2.35 (1.24) | 7.78 (2.85) | U=378.500 | <0.001* |
| Cannabis use frequency (days per month) | 10.58 (4.33) | 7.94 (5.27) | U=121.000 | 0.033* |
| Positive THC urine at baseline (n=37); %(n) | 83.33 (15) | 63.16 (12) | χ21=1.908 | 0.167 |
| Cannabis Abuse Screening Test | 6.45 (2.72) | 5.60 (3.56) | t38=0.848 | 0.402 |
| Cigarette use | ||||
| Ever used cigarettes; %(n) | 95.00 (19) | 75.00 (15) | χ21=3.137 | 0.077 |
| Age first tried cigarettes (years)b | 15.06 (1.49) | 17.21 (2.61) | U=279.000 | 0.003* |
| Duration of cigarette use (years) | 1.91 (1.41) | 7.60 (3.44) | U=356.500 | <0.001* |
| Cigarette use frequency (days per month) | 19.28 (12.36) | 10.37 (11.62) | U=120.500 | 0.030* |
| Cigarettes per day | 3.74 (2.83) | 1.84 (2.06) | U=107.500 | 0.011* |
| Fagerström Test for Nicotine Dependence | 1.30 (1.03) | 0.20 (0.70) | U=81.000 | <0.001* |
| Carbon monoxide at baseline (p.p.m.; n=38) | 6.00 (4.55) | 5.68 (3.96) | U=163.000 | 0.624 |
| Alcohol use | ||||
| Ever used alcohol; %(n) | 100.00 (20) | 100.00 (20) | NA | NA |
| Age first tried alcohol (years) | 14.07 (14.07) | 14.56 (3.22) | t28=-0.611 a | 0.546 |
| Duration of alcohol use (years) | 3.01 (1.63) | 10.93 (3.71) | U=399.000 | <0.001* |
| Alcohol use frequency (days per month) | 5.80 (4.83) | 9.78 (6.00) | U=283.500 | 0.023* |
| Alcohol units per typical drinking sessionc | 9.81 (6.92) | 8.43 (2.82) | U=190.000 | 0.799 |
| Alcohol Use Disorders Identification Test | 8.95 (5.53) | 8.95 (4.82) | U=214.000 | 0.718 |
Abbreviations: NA, not applicable; THC, tetrahydrocannabinol.
a
Levene's test for homogeneity of variance violated.
b
Calculated only on those who had ever used cigarettes (n=34).
c
Units used are standard UK units of alcohol; equivalent to 8 g of pure alcohol or ~3/5ths of a NIAAA standardized drink.
*P<0.05.
Values reflect mean (s.d.) unless otherwise stated; P-values reflect independent t-test comparing mean, Mann–Whitney U-test comparing median or chi-squared comparing frequency (as appropriate), by age group.