Not in meta‐analysis
Study	Outcome	Notes
Insufficient data
Lipman 1966	Target symptoms (doctor‐ and other observer‐reported outcomes)	Not enough data for meta‐analysis. Reports means and number of participants only. Standard deviation unclear. Qualitatively, no strong direction of benefit (active placebo: mean = 2.15, N = 99, standard placebo: mean = 2.17, N = 90).
Shader 1964	Revised Clyde Mood Scales (observer)	Not enough data for meta‐analysis. However, unclear if the relevant outcome reported in the trial has a clear directionality.
No relevant data
Berna 2017	No indication of a relevant outcome measured
Bjørkedal 2011	No indication of a relevant outcome measured	Measured laser‐evoked potentials with EEG recordings, including N2 and P2 amplitudes and latencies, to rule out the possible effects of response bias. We were uncertain whether they could be interpreted as clinically relevant observer‐reported outcomes of benefit and therefore did not use them for analysis.
Dellemijn 1997	No indication of a relevant outcome measured
Fangman 1963	No indication of a relevant outcome measured
Malmstrom 2006	No indication of a relevant outcome measured
Prosenz 2017	No indication of a relevant outcome measured	Measured sedation using bispectral index (BIS) and Richmond Agitation‐Sedation Scale (RASS) as well as psychomotor and executive functions using the Groton Maze Learning Test Task and the Detection Task. We decided that they were not clinically relevant observer‐reported outcomes of benefit and therefore did not use them for analysis.
Rief 2012	No indication of a relevant outcome measured
Woodrow 1988	No indication of a relevant outcome measured