The impact of adolescent stress on nicotine use and affective disorders in rodent models

Recent findings indicate that stress exposure during adolescence contributes to the development of both nicotine use and affective disorders, suggesting a potential shared biological pathway. One key system that may mediate the association between adolescent stress and nicotine or affective outcomes is the hypothalamic–pituitary–adrenal (HPA) axis. Here we reviewed evidence regarding the effects of adolescent stress on nicotine responses and affective phenotypes and the role of the HPA‐axis in these relationships. Literature indicates that stress, possibly via HPA‐axis dysfunction, is a risk factor for both nicotine use and affective disorders. In rodent models, adolescent stress modulates behavioural responses to nicotine and increases the likelihood of affective disorders. The exact role that the HPA‐axis plays in altering nicotine sensitivity and affective disorder development after adolescent stress remains unclear. However, it appears likely that adolescent stress‐induced nicotine use and affective disorders are precipitated by repetitive activation of a hyperactive HPA‐axis. Together, these preclinical studies indicate that adolescent stress is a risk factor for nicotine use and anxiety/depression phenotypes. The findings summarized here suggest that the HPA‐axis mediates this relationship. Future studies that pharmacologically manipulate the HPA‐axis during and after adolescent stress are critical to elucidate the exact role that the HPA‐axis plays in the development of nicotine use and affective disorders following adolescent stress. This review examines the preclinical literature on how adolescent stress influences nicotine use and affective disorders. A model is proposed where adolescent stress initiates HPA‐axis activation to enhance nicotine use which in turn potentiates HPA‐axis activation. This cyclical relationship ultimately leads to the development of affective disorders through heightened HPA‐axis responding/sensitivity.