Questions 6 and 7 relate to the following information (ADD study) Patients with depression who do not respond to a first or second treatment with anti-depressants are characterised as having treatment refractory depression (TRD). A Cochrane review suggested that co- treatment with an antiglucocorticoid such as metryapone may be effective in treating TRD. The following study aimed to investigate this co-treatment: . Study protocol for the randomised controlled trial: Antiglucocorticoid augmentation of anti-depressants in depression (The ADD study), McAllister-Williams R.H., et al, BMC Psychiatry (2013) 12:205. https://doi.org/10.1189/1471-244X-13-205 => Methods/design Patients with moderate to severe treatment refractory Major Depression aged 18 to 65 will be randomised to metyrapone 500 mg twice daily or placebo for three weeks, in addition to on-going conventional serotonergic antidepressants. The primary outcome will be improvement in Montgomery-Asberg Depression Rating Scale score five weeks after randomisation (i.e. two weeks after trial medication discontinuation). Secondary outcomes will include the degree of persistence of treatment effect for up to 6 months, improvements in quality of life and also safety and tolerability of metyrapone. The ADD Study will also include a range of sub-studies investigating the potential mechanism of action of metyrapone. Sample size, power and effect size The primary outcome measure is change in MADRS between weeks 0 and +5. The effect size for this measure in the Jahn study [33] was 0.63. The study has been powered around the more conservative moderate effect size of 0.5 which, assuming a post-intervention standard deviation of 12 points [33], corresponds to a six point difference on the MADRS. What sample size would be required at analysis to detect the effect with 90% power, assuming alpha=5%? Note: depending on the method used (formulas, PSPower, Stata), your answer may differ slightly. Select the closest option. O 54 per group 64 per group 85 per group 12106 per group