Date of Award

Fall 2018

Degree Type


Degree Name

Doctor of Philosophy (PhD)



Committee Chair

Alen Hajnal

Committee Chair School


Committee Member 2

Mark Huff

Committee Member 2 School


Committee Member 3

Richard Mohn

Committee Member 3 School


Committee Member 4

Adam Collier


Placebo responses are a widely observed phenomenon in humans and animals alike. In humans, placebo responses are largely attributed to expectancy processes, and conditioning (Stewart-Williams, & Podd, 2004). In the clinical setting, the placebo response is very useful as it has the power to improve physical and/or psychological states, without the need for treatment with a higher drug dose. In clinical trials however, researchers must control for potential placebo effects. Still, despite the experimental control, placebo responses are widely observed during phase 2 and phase 3 clinical trials, resulting in a weak drug effect. In the effort to improve the efficiency of drug discovery and development, it is necessary to better understand the placebo response. The current study tested a protocol that examined the existence of placebo responses in chronically stressed adult zebrafish. Over a 30 day period, animals were subjected to an unpredictable chronic mild stress (UCMS) procedure (Piato et al., 2011). Concurrent with the UCMS protocol, stressed animals were conditioned to receive antidepressant (fluoxetine) treatment in a visually distinct arena to protect against stress in the zebrafish. The conditioned placebo response was then evaluated in the novel tank test following the placebo session (treatment with system water). Exposure to the placebo dose produced a slight anxiety-like response and this compensatory response has been observed in different domains of drug conditioning, supporting the conditioning model. The results of this study contribute to our current understanding of the placebo responses in animal models, specifically in a stressed animal model.