Fig. 2.

Power to reject the null hypothesis in hypotheses A1, A2, C1, and C2, based on different strengths of association with lHCV and rHCV. Displayed power curves were calculated based on age to HCV associations of r = -0.37 (lHCV) and r = -0.40 (rHCV), as detected by Erickson and colleagues (2010). Considering the relative uncertainty regarding which effect sizes may be expected in our hypotheses, particularly regarding age moderation effects, we simulated power for a range of possible effect sizes. The plots illustrate to which magnitude of effects our analyses will be sensitive, given our fixed prospective sample sizes of 301 (basal sBDNF) and 113 (reactive sBDNF). Red vertical dashed lines indicate the assumed effect strength for lHCV (r = 0.19), and solid dark blue lines correspond to the assumed effect strength for rHCV (r = 0.14). While data was modelled separately for lHCV and rHCV, the simulated models evaluated effects on total HCV. The code as well as the model summary data used to generate the above images can be accessed at the Open Science Framework (https://osf.io/3p7da/). lHCV, left hippocampal volume; rHCV, right HCV; sBDNF, serum brain-derived neurotrophic factor.