Prevalence of cannabis use, tobacco smoking and respiratory symptoms at each assessment
| Assessment age years | |||||
| 18 | 21 | 26 | 32 | 38 | |
| Cannabis use# | 934 | 956 | 976 | 968 | 948 |
| Frequent | 81 (9) | 157 (16) | 162 (17) | 138 (14) | 99 (10) |
| Occasional | 337 (36) | 339 (35) | 327 (34) | 222 (23) | 146 (15) |
| Change in cannabis use¶ | 934 | 946 | 957 | 939 | |
| Nonuser | 768 (82) | 736 (78) | 768 (80) | 793 (84) | |
| Quitter | 26 (3) | 52 (6) | 54 (6) | 50 (5) | |
| Starter | 85 (9) | 56 (6) | 35 (4) | 12 (1) | |
| Continuing | 55 (6) | 102 (11) | 100 (10) | 84 (9) | |
| Tobacco smoking | 868 | 946 | 969 | 972 | 957 |
| Current | 284 (33) | 347 (37) | 352 (36) | 343 (35) | 253 (26) |
| Symptoms | |||||
| Cough | 120/868 (14) | 125/946 (13) | 176/972 (18) | 165/968 (17) | 132/947 (14) |
| Sputum | 108/868 (12) | 132/946 (14) | 170/972 (17) | 142/966 (15) | 91/946 (10) |
| Wheeze | 276/868 (32) | 390/957 (41) | 356/972 (37) | 266/972 (27) | 248/948 (26) |
| Dyspnoea | 206/868 (24) | 320/946 (24) | 219/970 (23) | 177/962 (18) | 190/946 (20) |
Data are presented as n, n (%) or n/N (%). Differences in n-values at each age and denominators for prevalences reflect missing data among active study participants. #: frequent cannabis use was defined as ≥52 times in the previous year (weekly); occasional cannabis use was defined as between one and 51 occasions in the previous year. ¶: changes in cannabis use are changes in reported frequent use since the previous assessment.