Figure 1.
The effect of cognitive therapy versus ‘no intervention’ at cessation of treatment on Hamilton Rating Scale for Depression (HDRS).
Below figure: All four trials used only individual cognitive therapy. The therapists' level of experience and/or education was classified as ‘high’ in Dozios (2009), as ‘intermediate’ in Murphy (1984) and Hollon (1992), and as ‘unclear’ in Scott (1997).
Table 1.
Characteristics of the included trials.
Table 2.
Risk of bias.
Figure 2.
The effect of cognitive therapy versus ‘no intervention’ at cessation of treatment on Becks Depression Inventory (BDI).
Figure 3.
Trial sequential analysis of the cumulative meta-analysis of the effect of cognitive therapy versus ‘no intervention’ for major depressive disorder on the Hamilton Rating Scale for Depression (HDRS).
Below figure: The required information size of 994 is calculated based on an intervention effect compared with ‘no intervention’, of 2 points on the HDRS, a variance of 126.5.04 on the mean difference, a risk of type I error of 5%, and a power of 80%. With these presumptions, the cumulated Z-curve (blue curve) do not cross the trial sequential monitoring boundaries (red inner sloping lines) implying that there is no firm evidence for a beneficial effect of cognitive therapy compared with no intervention.
Figure 4.
Trial sequential analysis of the cumulative meta-analysis of the effect of cognitive therapy versus no ‘intervention’ for major depressive disorder on the Beck Depression Inventory (BDI).
Below figure: The required information size of 570 is calculated based on an intervention effect compared with ‘no intervention’, of 4 points on the BDI, a variance of 153.1 on the mean difference, a risk of type I error of 1% and a power of 90%. With these presumptions, the cumulated Z-curve (blue curve) crosses the trial sequential monitoring boundaries (red inner sloping lines) implying that there is no risk of random error in the estimate of a beneficial effect of cognitive therapy compared with no intervention. However, all trials were considered as high risk of bias, which could explain the positive findings.
Figure 5.
Effect of cognitive therapy versus ‘no intervention’ on ‘no remission’ (HDRS>7) at cessation of treatment.
Figure 6.
Trial sequential analysis of the cumulative meta-analysis of the effect of cognitive therapy versus no ‘intervention’ for no remission according to the Hamilton Rating Scale for Depression.
Below figure: The required information size of 303 is calculated based on a control event proportion of 62%, an assumed relative risk reduction of 30%, a type I error of 5%, a beta of 10% (power of 90%), and the heterogeneity in the meta-analysis. With these presumptions, the cumulated Z-curve (blue curve) do not cross the trial sequential monitoring boundaries (red inner sloping lines) implying that there is a risk of random error in the estimate of a beneficial effect of cognitive therapy compared with no intervention, either due to sparse data or repetitive testing in the cumulative meta-analysis. Furthermore, all trials were considered as high risk of bias, which could explain the positive findings in the conventional meta-analysis.