66: Adolescent behavior and Hypothalamic Pituitary Adrenal (HPA) axis function

Methodologic issues in using salivary cortisol


      Research in psychoneuroendocrinology (PNE) has burgeoned in the last twenty years. This is particularly true for research on stress, the HPA axis, and adolescent development and behavior. Moreover, advances in data collection and assay techniques have decreased the invasiveness of measuring HPA axis function. As a result, researchers studying behavior or development in adolescents often now obtain saliva cortisol as part of their protocols. However, in many published studies, there is inadequate integration of the current knowledge of HPA axis physiology and techniques in measuring salivary cortisol. The overarching purpose of this presentation is to update the audience about the most valid methods for measuring HPA axis function in adolescent PNE research.


      Three searches were conducted of the medical literature, using PubMed, Medline, and Psychological Abstracts. All searches used the timeframe of 1966-August, 2005. The first one focused on papers presenting data or reviews about HPA axis physiology in adolescents (including data on the effects of puberty, development, etc.). The second searched for data on the techniques for obtaining saliva and measuring cortisol in this body fluid. The third search looked for any study that had measured cortisol levels in saliva and had investigated adolescent development or behavior. Data from the first two searches were critically reviewed and integrated to create criteria for valid protocols when measuring HPA axis function in PNE studies of adolescents. These criteria were then used to evaluate the studies to date that have used measured saliva cortisol in adolescents.


      Few of the protocol criteria suggested by the literature review were used in most of the studies to date. The level of conformity to the criteria was correlated with the study publication date, but a high proportion of the studies published in the last five years still had only modest adherence to the protocol criteria.


      A high proportion of the extant studies of PNE and development or behavior in adolescents have used sub-optimal protocols for assessing HPA axis function with salivary cortisol. This raises questions about the validity and generalizability of the results. The most likely explanation is that the information currently available was not known during the earlier studies. However, many of the studies were conducted after the data on HPA axis physiology and salivary cortisol techniques were published. The more likely explanation is that the data are published in such a diverse set of journals that they are difficult for any one researcher to synthesize. To address this problem, the presentation closes with guidelines for obtaining physiologically valid measurements of HPA axis function in adolescents, using salivary cortisol.


      NIMH: 1RO1 MH066003 (Pajer, PI).