Table 3.
Descriptive Data (Absolute Counts and Rate of Offences Per 1000 Person Years of Observation) for Overall, Violent, and Nonviolent Offences for Olanzapine (n = 2258) and Clozapine Treatment (n = 1004)
| Clozapine | Olanzapine | Interaction Term | P Value for Interaction | |||
|---|---|---|---|---|---|---|
| Total number of violent offences | 103 | 506 | ||||
| Individuals with any violent offence (percentage of the overall treatment group) | 63 (6.27) | 144 (6.38) | ||||
| Number of violent offences before treatment (rate) | 96 (74.41) | 376 (95.71) | ||||
| Number of violent offences during treatment (rate) | 7 (5.43) | 130 (33.09) | ||||
| Effect of drug on violent offence rate | RR | 95% CI | RR | 95% CI | ||
| Crude | 0.07 | 0.03, 0.18 | 0.35 | 0.20, 0.61 | ||
| Fully adjusteda | 0.13 | 0.05, 0.34 | 0.82 | 0.47, 1.43 | 4.82 (1.56,14.86) | P = .002 |
| Total number of nonviolent offences | 222 | 507 | ||||
| Individuals with any nonviolent offence (percentage of the overall treatment group) | 69 (6.87) | 193 (8.55) | ||||
| Number of nonviolent offences before treatment (rate) | 161 (124.79) | 326 (82.99) | ||||
| Number of nonviolent offences during treatment (rate) | 61 (47.28) | 181 (46.07) | ||||
| Effect of drug on nonviolent offence rate | RR | 95% CI | RR | 95% CI | ||
| Crude | 0.38 | 0.17, 0.83 | 0.56 | 0.40, 0.76 | ||
| Fully adjusteda | 0.37 | 0.17, 0.80 | 0.61 | 0.44, 0.86 | 1.66 (0.68,4.04) | P = .263 |
| Total number of overall offences | 369 | 960 | ||||
| Individuals with any overall offence (percentage of the overall treatment group) | 128 (12.75) | 304 (13.46) | ||||
| Number of overall offences before treatment (rate) | 295 (122.69) | 635 (161.64) | ||||
| Number of overall offences during treatment (rate) | 74 (30.78) | 325 (82.73) | ||||
| Effect of drug on overall offence rate | RR | 95% CI | RR | 95% CI | ||
| Crude | 0.25 | 0.12, 0.51 | 0.51 | 0.12, 0.51 | ||
| Fully adjusteda | 0.24 | 0.12, 0.48 | 0.62 | 0.45, 0.85 | 2.55 (1.20,5.44) | P = .015 |
Also shown are crude and adjusted offence (overall, nonviolent, and violent) rate ratios with 95% confidence intervals for during vs before treatment with clozapine and olanzapine. Rate ratios were estimated from zero-inflated negative binomial regression models with offence rate as the dependent variable and period of observation (dichotomized into before treatment and during treatment), as the main independent variable of interest. Models took account of clustered before and during treatment data within individuals. Model estimates for zeroes are presented in supplementary table S1.
aFully adjusted models are adjusted for urban residence, salary presence, employment status, and unemployment benefit receipt.