Date of Award


Degree Type


Degree Name

Doctor of Philosophy in Psychology



First Advisor

Joseph S. Rossi


In the mid seventies, Robert Ader and Nicholas Cohen (1975) conducted and published a series of experiments that are generally recognized as a major turning point for the behavioral and physical sciences. In classical conditioning experiments, Ader and Cohen were able to weaken the immune system reaction against foreign material in rats. The experiments demonstrated that the "self-regulating and autonomous" immune system was vulnerable to behavioral factors. These experiments seemed to galvanize a community of scientists who had hypothesized like scientists and philosophers before them the role of emotional states in influencing physiological processes.

The preeminent discipline which has evolved in this dynamic field of study is psychoneuroimmunology. Being an interdisciplinary field, it has begun to study extensively the role of psychological and behavioral factors in physiological processes, namely the immune and endocrine systems. The implications of this research could have a profound impact on the major, complex diseases which plague the health profession. Since the mid seventies, a plethora of research focused on the relationship between psychological/behavioral events and the immune system. Although there have been many narrative reviews of the literature, there have been only a few meta-analyses performed.

The objective of this investigation was to procure all research that focused on the psychological modulation of the immune system in humans and to measure the magnitude of effect of the psychological factors in each study. In addition, 7 unique characteristics (predictors) of the studies included in the meta-analysis were analyzed to determined if they covaried significantly with study outcomes. These results would shed light on the analytical questions of explanation and prediction.

For the meta-analysis, 75 statistical tests were transformed into common metrics: Z scores and one-tailed probability levels for the significance level and product-moment correlation's, Fisher'Zs and Cohen's d for effect size. The results of the analysis indicated small to large effect sizes for individual statistical tests. When tests were grouped according to type of immunologic measure (innate, humeral or cellular immunity), slightly stronger results were obtained.

The 7 characteristics were publication date, type of population, validity, experiment situation, type of treatment, and direction of modulation. The results of the analyses indicated that the characteristics or predictors covaried significantly with study outcomes.



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