For further details on EEG assessment by the individual groups, see supplementary material. Recording methods differed between the five included cohorts on sampling frequency, causal filter settings, and reference electrode (for COGA cohorts). Although these settings are likely to affect the recorded power values, they are also very unlikely to affect the rank ordering of power values between subjects. Since cohorts were meta‐analyzed using p‐values rather than inverse variance, these effects were automatically discarded, and therefore limiting concern regarding the heterogeneity introduced by recording differences across cohorts.
