UNIVERSITY OF CALGARY

UNIVERSITY OF CALGARY
Light Therapy for Post-Treatment Cancer-Related Fatigue: An Investigation of Impact on
Psychological Outcomes and Biological Mechanisms
by
Jillian Angela Johnson
A THESIS
SUBMITTED TO THE FACULTY OF GRADUATE STUDIES
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY
GRADUATE PROGRAM IN PSYCHOLOGY
CALGARY, ALBERTA
SEPTEMBER, 2016
© Jillian Angela Johnson 2016

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Abstract
OBJECTIVE: To investigate the impact of a one-month light therapy intervention on symptoms
of fatigue, psychological outcomes, and diurnal cortisol rhythms in cancer survivors with clinical
fatigue.
METHODS: Adult cancer survivors who met diagnostic criteria for cancer-related fatigue were
eligible and randomized to receive either bright white light (BWL) or an active comparator (dim
red light; DRL). Participants used the device for 30 minutes upon waking for 4 weeks. Baseline
and post-intervention assessments of fatigue, mood disturbance, depression, sleep quality, and
quality of life were obtained. Participants also provided four saliva samples per day over a period
of 3 days both before and after the intervention. Linear mixed-model (LMM) analysis with
random slopes and intercepts were conducted on the primary outcome of fatigue, and generalized
estimating equations were employed to investigate the secondary psychological outcomes.
Cortisol slopes, total cortisol output (area under the curve), and cortisol output at four sampling
times were examined for time, group, and interaction effects using LMM analyses.
RESULTS: Eighty-one participants were randomized to either BWL (n=42) or DRL (n=39). The
light therapy intervention was acceptable as evidenced by high adherence rates and low dropout
(2.5%). Overall, participants in the BWL condition displayed greater improvements in symptoms
of fatigue than those in the DRL condition (d=.30). Both groups showed improvements on
symptoms of mood disturbance, depression, sleep quality, and quality of life over time. A
subsample of participants (n=77) were included in the cortisol analyses. Cortisol slope and total
cortisol output were unchanged after the intervention, but an increase in output was observed in
both groups at the post-intervention noon sample, as well as decreased output at the post-
intervention 5pm sample in the BWL condition.

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CONCLUSION: Early morning exposure to bright white light resulted in improvements in
symptoms of fatigue in cancer survivors with clinical fatigue. These findings, along with those of
previous research of light therapy in cancer patients and survivors, support the use of light
therapy for cancer-related symptoms. Furthermore, light therapy has the potential to impact the
diurnal release of cortisol, though further research into the associations with symptoms of fatigue
are required.
Keywords: cancer, cancer-related fatigue, randomized controlled trial, mood, quality of
life, diurnal cortisol

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Acknowledgements
First, I would like to extend sincere gratitude to my mentors, Dr. Tavis Campbell and Dr.
Linda Carlson, for their constant and unwavering encouragement, guidance, and support
throughout my graduate training. I am forever grateful for the time and energy you have both
dedicated to ensuring my success. I would also like to extend a special thank you to Dr. Sheila
Garland for her support with this project and for her guidance and advice.
Thank you to all of the participants who dedicated so much time and energy to being a
part of the study. To my fellow colleagues, past and present, in the Behavioral Medicine Lab and
the Department of Psychosocial Resources, thank you for all of the emotional support and words
of encouragement. To my husband and family, thank you for believing in me and following me
on this adventure. Finally, thank you to the examination committee members for dedicating their
time to review this document and take part in the examination.
This project was funded by the Canadian Cancer Society. I would also like to
acknowledge the following funding agencies for the scholarships and awards that afforded me
the opportunity to pursue this graduate training: Alberta-Innovates Health Solutions, the Alberta
Cancer Foundation, the Killam Trust, and the Lloyd and Florence Cooper Doctoral Scholarship
in Integrative Medicine.

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Dedication
I dedicate this thesis to all of the participants who graciously donated their time to be a part of
this study. The success of this trial was due to your unwavering dedication and commitment.
Thank you for sharing your time and stories with me.