Multiple multilevel meta-regression model for placebo response on the aggregate measure of internalising symptoms
| o/k (n) | SMD | 95% CI | P value | |
| Main disorder | ||||
| GAD (index) | 79/26 (3407) | – | – | – |
| Panic | 94/17 (1895) | 0.64 | 0.25 to 1.04 | 0.001* |
| SAD | 82/22 (2186) | 0.34 | −0.07 to 0.75 | 0.107 |
| PTSD | 51/12 (936) | 0.18 | −0.27 to 0.64 | 0.43 |
| OCD | 52/15 (1050) | 0.72 | 0.25 to 1.18 | 0.002* |
| More than one anxiety disorder | 5/3 (158) | 0.15 | −0.62 to 0.93 | 0.70 |
| Sample age group | ||||
| Adults/elderly (index) | 311/79 (8567) | – | – | – |
| Children/adolescents | 52/16 (1065) | −0.27 | −0.74 to 0.19 | 0.24 |
| Sampling | ||||
| Outpatients (index) | 282/76 (7575) | – | – | – |
| Community | 9/3 (305) | 0.20 | −0.47 to 0.87 | 0.55 |
| Mixed | 15/5 (516) | 0.38 | −0.16 to 0.92 | 0.16 |
| Unclear | 57/11 (1236) | 0.11 | −0.27 to 0.49 | 0.56 |
| Concomitant benzodiazepine use | ||||
| No (index) | 190/52 (6277) | – | – | – |
| Not informed | 89/24 (2147) | 0.16 | −0.15 to 0.48 | 0.31 |
| Unclear | 13/3 (341) | 0.86 | −0.12 to 1.84 | 0.08 |
| Yes | 71/16 (867) | 0.01 | −0.37 to 0.41 | 0.92 |
| Placebo lead-in period | ||||
| No (index) | 131/37 (2979) | – | – | – |
| Not informed | 24/12 (1104) | 0.09 | −0.34 to 0.52 | 0.70 |
| Unclear | 8/1 (90) | −0.55 | −1.49 to 0.39 | 0.25 |
| Yes | 200/16 (867) | 0.44 | 0.10 to 0.78 | 0.01* |
| Time to outcome measure (weeks) | ||||
| 12–14 (index) | 172/45 (4794) | – | – | – |
| 6–8 | 78/23 (1797) | −0.25 | −0.63 to 0.12 | 0.19 |
| 9–11 | 94/24 (2646) | −0.0823 | −0.40 to 0.24 | 0.61 |
| 15–17 | 5/1 (157) | 0.7110 | −0.25 to 1.68 | 0.15 |
| 18–20 | 7/1 (69) | −0.1333 | −0.95 to 0.68 | 0.75 |
| 21–26 | 7/1 (168) | −1.3408 | −2.78 to 0.09 | 0.06 |
| Data analysis method | ||||
| Mixed, hierarchical or random models (index) | 31/6 (499) | – | – | – |
| Completers | 10/4 (173) | 0.35 | −0.44 to 1.14 | 0.39 |
| Last observation carried forward | 309/81 (8837) | 0.26 | −0.18 to 0.71 | 0.25 |
| Unclear | 13/4 (123) | 0.25 | −0.48 to 0.99 | 0.49 |
| Study funding source | ||||
| Academic (index) | 22/7 (589) | – | – | – |
| Industry | 280/71 (7997) | 0.36 | −0.10 to 0.82 | 0.13 |
| Governmental or non-profit | 26/8 (332) | 0.32 | −0.34 to 0.98 | 0.34 |
| Unclear | 35/9 (714) | 0.17 | −0.36 to 0.70 | 0.53 |
| Number of sites | ||||
| Single centre (index) | 59/16 (434) | – | – | – |
| Multicentre | 304/79 (9198) | −0.34 | −0.73 to 0.04 | 0.08 |
| Comparator | ||||
| Head-to-head (index) | 23/8 (1040) | – | – | – |
| Different dose | 56/15 (1704) | 0.41 | −0.07 to 0.90 | 0.09 |
| Placebo | 284/72 (6914) | 0.18 | −0.65 to 1.02 | 0.67 |
| Number of drug arms | ||||
| 1 (index) | 288/73 (7008) | – | – | – |
| 2 | 22/9 (1259) | −0.24 | −0.99 to 0.51 | 0.52 |
| 3 | 53/13 (1365) | −0.59 | −1.31 to 0.13 | 0.11 |
| Sample size at baseline | 263/95 (9632) | −0.002 | −0.003 to 0.0003 | 0.09 |
| Number of visits | 263/95 (9632) | 0.003 | −0.07 to 0.07 | 0.91 |
| Publication year | 263/95 (9632) | −0.02 | −0.05 to 0.008 | 0.16 |
| Baseline severity of symptoms | 263/95 (9632) | −0.0003 | −0.003 to 0.003 | 0.84 |
*Significant differences.
GAD, generalised anxiety disorder; k, number of studies; n, sample size; o, number of outcome measures; OCD, obsessive-compulsive disorder; PTSD, post-traumatic stress disorder; SAD, social anxiety disorder; SMD, standardised mean difference.