Table 3.
Unadjusted odds ratios and 95% confidence intervals reflecting unadjusted within-pair associations between aspects of cannabis use and suicidal thoughts and behaviours, separately, in discordant monozygotic and dizygotic same-sex twin pairs.
| Discordant for Early Cannabis Use (Co – twin is never or later – onset user) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| DZ | MZ | |||||||||
| Dependent Variable | OR | 95% CI | χ2 | p | N pairs | OR | 95% CI | χ2 | p | N pairs |
| Major Depressive Disorder | 1·816# | (1·22, 2·70) | 8·72 | 0·0031 | 293 | 1·344# | (0·85, 2·12) | 1·60 | 0·2057 | 260 |
| Suicidal ideation | 2·233# | (1·45, 3·44) | 13·38 | 0·0003 | 271 | 1·500# | (0·91, 2·46) | 2·56 | 0·1093 | 241 |
| Suicidal ideation lasting >1 day | 4·000 | (1·93, 8·30) | 13·84 | 0·0002 | 271 | 1·667 | (0·82, 3·41) | 1·96 | 0·1618 | 241 |
| Suicide plan | 2·800 | (1·36, 5·76) | 7·81 | 0·0052 | 271 | 1·167 | (0·54, 2·52) | 0·15 | 0·6952 | 241 |
| Suicide attempt | 6·500 | (2·27, 18·62) | 12·15 | 0·0005 | 316 | 1·900 | (0·88, 4·09) | 2·70 | 0·1004 | 278 |
| Discordant for Early Cannabis Use (co-twin is later – onset user) | ||||||||||
| DZ | MZ | |||||||||
| Dependent Variable | OR | 95% CI | χ2 | p | N pairs | OR | 95% CI | χ2 | p | N pairs |
| Major Depressive Disorder | 1·467 | (0·92, 2·33) | 2·62 | 0·1058 | 194 | 1·545 | (0·90, 2·64) | 2·53 | 0·1116 | 194 |
| Suicidal ideation | 2·238# | (1·34, 3·74) | 9·42 | 0·0021 | 176 | 1·350# | (0·76, 2·41) | 1·03 | 0·3090 | 178 |
| Suicidal ideation lasting >1 day | 4·000 | (1·64, 9·79) | 9·22 | 0·0024 | 176 | 1·556 | (0·67, 3·59) | 1·07 | 0·3011 | 178 |
| Suicide plan | 2·125 | (0·92, 4·92) | 3·09 | 0·0787 | 176 | 1·444 | (0·62, 3·38) | 0·72 | 0·3964 | 178 |
| Suicide attempt | 5·333# | (1·55, 18·30) | 7·08 | 0·0078 | 214 | 2·000# | (0·75, 5·33) | 1·92 | 0·1657 | 209 |
| Discordant for Frequent (≥ 100 times; co – twin never user or lighter user) | ||||||||||
| DZ | MZ | |||||||||
| Dependent Variable | OR | 95% CI | χ2 | p | N pairs | OR | 95% CI | χ2 | p | N pairs |
| Major Depressive Disorder | 2·115# | (1·33, 3·37) | 9·91 | 0·0016 | 252 | 1·720# | (1·05, 2·82) | 4·65 | 0·0311 | 199 |
| Suicidal ideation | 2·630# | (1·69, 4·10) | 18·29 | <0·0001 | 241 | 2·714# | (1·47, 5·01) | 10·20 | 0·0014 | 190 |
| Suicidal ideation lasting >1 day | 3·500# | (1·60, 7·68) | 9·77 | 0·0018 | 241 | 3·143# | (1·34, 7·36) | 6·96 | 0·0083 | 190 |
| Suicide plan | 1·636 | (0·77, 3·47) | 1·66 | 0·1982 | 241 | 2·143 | (0·87, 5·26) | 2·77 | 0·0959 | 190 |
| Suicide attempt | 4·400# | (1·67, 11·62) | 8·94 | 0·0028 | 276 | 2·286# | (0·94, 5·56) | 3·33 | 0·0681 | 225 |
| Discordant for Frequent (≥ 100 times; co – twin is lighter user) | ||||||||||
| DZ | MZ | |||||||||
| Dependent Variable | OR | 95% CI | χ2 | p | N pairs | OR | 95% CI | χ2 | p | N pairs |
| Major Depressive Disorder | 1·696# | (1·01, 2·84) | 4·03 | 0·0446 | 174 | 1·947# | (1·12, 3·39) | 5·58 | 0·0182 | 156 |
| Suicidal ideation | 2·842# | (1·69, 4·79) | 15·33 | <0·0001 | 165 | 2·909# | (1·47, 5·77) | 9·33 | 0·0022 | 147 |
| Suicidal ideation lasting >1 day | 4·000# | (1·50, 10·66) | 7·69 | 0·0056 | 165 | 3·600# | (1·34, 9·70) | 6·42 | 0·0113 | 147 |
| Suicide plan | 1·000 | (0·40, 2·52) | 0·00 | 1·0000 | 165 | 2·200 | (0·76, 6·33) | 2·14 | 0·1438 | 147 |
| Suicide attempt | 6·500# | (1·47, 28·80) | 6·07 | 0·0137 | 192 | 2·400# | (0·85, 6·81) | 2·71 | 0·1000 | 182 |
#
The 95% Confidence Intervals for these estimates overlap indicating equality of effect sizes, despite p-values. Table S3 for bootstrapped CI.