rates of internalizing and externalizing symptoms peak in adolescence as compared with childhood and adulthood, and such high rates of co-occurrence may obscure the unique effects of internalizing symptoms during adolescence. This makes detection of internalizing processes as defined solely by the marker of internalizing symptoms difficult during adolescence. In contrast, we take a developmental perspective that defines the risk associated with internalizing symptoms as a history of behaviors characterized by the internalizing pathway rather than simply rates of internalizing symptoms in adolescence. As such, we posit that internalizing symptoms that onset early and persist into adulthood may be a unique predictor of substance involvement and disorder after controlling for co-occurring externalizing symptoms.
