Table 2.
Measure of cannabis use and ORs for psychotic disorders for case-control sample across 11 sites
| Controls (n=1237) | Cases (n=901) | p value* | Crude OR (95% CI)† | p value | Fully adjusted OR (95% CI)† | p value | ||
|---|---|---|---|---|---|---|---|---|
| Lifetime cannabis use‡ | .. | .. | <0·0001 | |||||
| No | 650 (52·5%) | 303 (33·6%) | .. | 1 (ref) | .. | 1 (ref) | .. | |
| Yes | 574 (46·4%) | 585 (64·9%) | .. | 2·45 (2·0–2·9) | <0·0001 | 1·3 (1·1–1·6) | 0·0225 | |
| Currently using cannabis | 132 (10·7%) | 198 (22·0%) | 0·00349 | 2·7 (2·1–3·5) | <0·0001 | 1·1 (0·9–1·5) | 0·36 | |
| First used cannabis age ≤15 years old | 169 (13·7%) | 257 (28·6%) | <0·0001 | 3·9 (3·0–4·9) | <0·0001 | 1·6 (1·1–2·1) | 0·0122 | |
| Lifetime frequency of use | .. | .. | <0·0001 | |||||
| Never or occasional use | 1061 (85·8%) | 528 (58·7%) | .. | 1 (ref) | .. | 1 (ref) | .. | |
| Used more than once a week | 92 (7·4%) | 107 (11·9%) | .. | 2·5 (1·9–3·5) | <0·0001 | 1·4 (1·0–2·0) | 0·066 | |
| Daily use | 84 (6·8%) | 266 (29·5%) | .. | 6·2 (4·8–8·2) | <0·0001 | 3·2 (2·2–4·1) | <0·0001 | |
| Spent at least €20 per week on cannabis | 40 (3·2%) | 156 (17·4%) | <0·0001 | 5·6 (4·0–7·7) | <0·0001 | 2·5 (1·6–3·8) | <0·0001 | |
| Lifetime use of cannabis by potency§ | .. | .. | <0·0001 | |||||
| Low potency (THC <10%) | 331 (26·7%) | 251 (27·9%) | .. | 2·0 (1·6–2·5) | <0·0001 | 1·1 (0·9–1·5) | 0·38 | |
| High potency (THC ≥10%) | 240 (19·4%) | 334 (37·1%) | .. | 3·2 (2·6–4·0) | <0·0001 | 1·6 (1·2–2·2) | 0·0032 | |
Crude ORs are adjusted only for age, gender, and ethnicity whereas fully adjusted ORs are additionally adjusted for level of education, employment status, tobacco, stimulants, ketamine, legal highs, and hallucinogenics. OR=odds ratio. THC=Δ9-tetrahydrocannabinol.
*
p value for χ2 test.
†
Reference group for both crude and adjusted ORs is the never users unless specified otherwise.
‡
Data were missing for 13 individuals in each group.
§
Data were missing for three controls.