Consistent with human research suggesting that stress may influence the carcinogenic process, data from infrahuman experiments have revealed that aversive insults may potentiate or inhibit tumorigenicity, with nature of the change dependent on psychological, experiential, and organismic variables. Exacerbation of tumor growth is evident following acute exposure to uncontrollable but not controllable stress, and the effects of aversive stimuli vary as a function of prior stress history and social housing conditions. The fact that stress influences neurochemical, hormonal, and immunological functioning and that these changes are subject to many of the same manipulations that influenced the carcinogenic process suggests a relation between these 3 mechanisms and the stress-induced alterations of tumor growth. This contention is supported by findings showing that pharmacological manipulations that modify these endogenous substrates have predictable effects on tumorigenesis.(10¼ p ref)(PsycINFO Database Record (c) 2016 APA, all rights reserved)