Table 4.
Subgroup analyses to explore potential causes of heterogeneity among included studies
| Outcome | Subgroups | Between group heterogeneity | Effect size with confidence intervals and heterogeneity (I2) per subgroup | Conclusion |
|---|---|---|---|---|
| Change in depression scores | Type of depression: primary or secondary | Significant (P=0.03) | Primary: Hedges’ g=0.62 (95% CI 0.39 to 0.84, I2=0.0%) Secondary: Hedges’ g=0.88 (95% CI 0.42 to 1.33, I2=0.0%) |
The effect size for reduction in depression post-intervention is larger in secondary depression studies, but both subgroups contain little statistical heterogeneity |
| Change in depression scores | Depression measure: MADRS, QIDS, or BDI | Significant (P=0.04) | MADRS: Hedges’ g=0.71 (95% CI 0.34 to 1.09, I2=27.5%) QIDS: Hedges’ g=0.52 (95% CI 0.21 to 0.83, I2=0.0%) BDI: Hedges’ g=0.88 (95% CI 0.42 to 1.33, I2=0.0%) |
Although studies using the patient reported QIDS and BDI questionnaires showed statistically significant effects for psilocybin, the point estimate for MADRS (clinician assessed) fell between the two The MADRS subgroup displayed a small degree of heterogeneity, whereas the QIDS and BDI subgroups did not |
| Change in depression scores | Psilocybin dosage: 10-15 mg or 20-25 mg | Not significant (P=0.36) | 10-15 mg: Hedges’ g=0.57 (95% CI 0.26 to 0.87, I2=0.0%) 20-25 mg: Hedges’ g=0.73 (95% CI 0.47 to 1.00, I2=0.0%) |
The two dosage groups did not appear to differentially affect the primary outcome, change in depression scores. Superior effect sizes seen in the higher dosage group should thus be interpreted with caution |
| Change in depression scores | Time of assessment post-psilocybin: 2-4 weeks or 4-8 weeks | Not significant (P=0.97) | 2-4 weeks: Hedges’ g=0.67 (95% CI 0.43 to 0.91, I2=0.0%) 4-8 weeks: Hedges’ g=0.67 (95% CI 0.25 to 1.08, I2=0.0%) |
The two time to assessment groups did not appear to differentially affect the primary outcome, change in depression scores |
| Response rate | Type of depression: primary or secondary | Not significant (P=0.09) | Primary: risk ratio 1.72 (95% CI 0.81 to 3.68, I2=37.0%) Secondary: risk ratio 3.44 (95% CI 0.05 to 24.50, I2=17.6%), based on two studies only |
There are insufficient data to conclude that response rate is affected by type of depression |
| Remission rate | Type of depression: primary or secondary | Not significant (P=0.11) | Primary: risk ratio 2.50 (95% CI 1.09 to 5.70, I2=7.8%) Secondary: risk ratio 4.52 (95% CI 0.17 to 11.70, I2=0.0%), based on two studies only |
There are insufficient data to conclude that remission rate is affected by type of depression |
I2=measure of heterogeneity.
BDI=Beck depression inventory; CI=confidence interval; MADRS=Montgomery-Åsberg depression rating scale; QIDS=quick inventory of depressive symptomatology.