The Comorbid Effects of Anxiety and Depressive Symptoms on COVID-19 Vaccine Hesitancy

Abstract

Background: Stringent public health interventions during the start of the COVID-19 pandemic highlighted the importance of vaccination as the exit strategy to return to normal life. Sociodemographic factors for vaccine hesitancy have been well established; however, literature on the psychological factors—namely anxiety and depressive symptoms—are limited and have conflicting results. This thesis studied the comorbid and independent effects of anxiety and depressive symptoms on vaccine hesitancy and explored time as an effect modifier for the relationships. Methods: Multi-wave national cross-sectional data collected by Mental Health Research Canada (MHRC) over the period of April 2021 to November 2021 was used for this study. GAD-7 and PHQ-9 were used to measure anxiety and depressive symptom levels, respectively. The prevalence of vaccine hesitancy was described. Multivariate logistic regression models were used to test the associations between anxiety/depressive symptoms and vaccine hesitancy, independently and then as an aggregate measure (psychological distress) to study the comorbid effects. Interaction analyses for the independent and comorbid effects model were done to test time as an effect modifier for the relationships of interest. Results: There were 11 232 participants for the independent effects analyses and 13 234 for the comorbid effects analyses. Vaccine hesitancy prevalence ranged from 26.8% in April 2021 to 7.4% by November 2021. Time was identified as an effect modifier for the independent effects of depressive symptoms and the comorbid effects of anxiety/depressive symptoms on vaccine hesitancy. Clinically significant anxiety symptoms were associated with vaccine hesitancy (OR=1.34, 95% CI: 1.12-1.59) but were not modified by time. Comorbid anxious depressed individuals were particularly affected in the month of August 2021 (OR=2.02, 95% CI: 1.44-2.83). Lower income and unemployment were associated with higher odds of vaccine hesitancy. Being 65+ years old and accessing mental health support were protective against vaccine hesitancy. Conclusions: Comorbid effects of anxiety/depressive symptoms on vaccine hesitancy were time-sensitive and coincided with the emergence of significant events during the COVID-19 pandemic. Further research is necessary to confirm these findings and test the issues of reverse causality and bidirectional association.