8.1 Weak instrument bias8.2 Allele scores8.3 Sample overlap8.4 Winner's curse8.5 Selection and collider bias8.6 Covariate adjustment8.7 Non-collapsibility8.8 Time and time-varying effects8.9 Power to detect a causal effect8.10 Choosing variants from a single gene region8.11 Binary exposure8.12 Alternative estimation methods8.13 Summary