The longitudinal association between externalizing behavior and frontoamygdalar resting‐state functional connectivity in late adolescence and young adulthood

BACKGROUND: Externalizing behavior has been attributed, in part, to decreased frontolimbic control over amygdala activation. However, little is known about developmental trajectories of frontoamygdalar functional connectivity and its relation to externalizing behavior. The present study addresses this gap by examining longitudinal associations between adolescent and adult externalizing behavior and amygdala–anterior cingulate cortex (ACC) and amygdala–orbitofrontal cortex (OFC) resting‐state functional connectivity in a sample of 111 typically developing participants aged 11–23 at baseline. METHODS: Participants completed two‐to‐four data waves spaced approximately two years apart, resulting in a total of 309 data points. At each data wave, externalizing behavior was measured using the Externalizing Behavior Broadband Scale from the Achenbach Youth/Adult Self‐Report questionnaire. Resting‐state fMRI preprocessing was performed using FSL. Amygdala functional connectivity was examined using AFNI. The longitudinal association between externalizing behavior and amygdala–ACC/OFC functional connectivity was examined using linear mixed effect models in R. RESULTS: Externalizing behavior was associated with increased amygdala–ACC and amygdala–OFC resting‐state functional connectivity across adolescence and young adulthood. For amygdala–ACC connectivity, externalizing behavior at baseline primarily drove this association, whereas for amygdala–OFC functional connectivity, change in externalizing behavior relative to baseline drove the main effect of externalizing behavior on amygdala–OFC functional connectivity. No evidence was found for differential developmental trajectories of frontoamygdalar connectivity for different levels of externalizing behavior (i.e., age‐by‐externalizing behavior interaction effect). CONCLUSIONS: Higher externalizing behavior is associated with increased resting‐state attunement between the amygdala and ACC/OFC, perhaps indicating a generally more vigilant state for neural networks important for emotional processing and control.