This study adds to the growing body of literature examining the impact of COVID-19 on mental health. Although several studies have explored the prevalence of depression during the pandemic, our study provides a unique contribution by examining the change in depression levels from before the pandemic to during the third wave in a Canadian context.

Our findings show a high prevalence of increased self-reported depression levels, with nearly half of the participants reporting an increase and over one-fifth reporting a substantial increase. These results are consistent with other studies that have used standardized depression screening tools. For example, a recent meta-analysis of 12 studies showed that the prevalence of depression during COVID-19 ranged from 18 to 33%, with a pooled estimate of 25%, compared to 3.44% prior to COVID-19 [22]. Other systematic reviews also showed similar trends among different populations [23, 24]. In Canada, a study evaluated the prevalence of major depressive disorders during COVID-19 and compared this to pre-COVID-19 estimated rates, reporting an increase from 7% before the pandemic to more than 13% during the pandemic [25]. However, there are also studies that have found no significant changes or even positive changes in mental health during the pandemic. For instance, a study in Norway found stable levels of mental disorders, suicidal ideation, and suicide deaths during the first six months of the COVID-19 pandemic compared to pre-pandemic levels, except for a decrease in mental disorders in the first pandemic period [19]. Overall, the inconsistency in the literature highlights the need for continued research to better understand the impact of the pandemic on mental health and to identify factors that may promote resilience and positive mental health outcomes.

Our results showed that perceived social isolation was the strongest and most consistent predictor of increased depression. Previous studies have shown that even short periods of isolation are linked to acute stress disorders [26], post-traumatic stress disorders [27], and depressive symptoms [28]. These psychological effects were still detected even three years later [27]. Furthermore, our study participants who had uncertainty about their ability to pay bills had a higher risk of experiencing increased depression after COVID-19. This finding is consistent with other [29]. Financial strain during a pandemic is usually due to pay cuts and financial loss without prior preparedness, representing a major threat to mental wellbeing. Prior research has shown that financial stress is associated with higher psychological distress, anxiety, and depression, irrespective of income [29, 30].

A common underlying factor that may explain the effects of both social isolation and financial strains on depression is uncertainty and intolerance to uncertainty. Individuals want to fully understand the extent of the threats they face and need to feel in control. Fear of the unknown and loss of control, since even experts cannot predict what comes next, is distressing. This can cause a sense of negativity that is detrimental to mental wellbeing. Our study also showed that fear of contracting COVID-19 was significantly associated with increased levels of depression. This implies that the intense fear of catching COVID-19 may cause a physiological response.

The results of our study demonstrate a significant interactive effect between fear of catching COVID-19 and financial constraint due to the pandemic on mental health outcomes. Our findings emphasize the potential for stressors to interact and exacerbate their impact on mental health during a pandemic. Specifically, fear of catching COVID-19 may increase anxiety and stress levels, which can be further compounded by financial constraint due to job loss or reduced income. Individuals who are already experiencing financial strain may also worry about the potential financial impact of contracting the virus, such as medical bills or lost income from time off work. These findings highlight the need for interventions that consider the potential interplay between different stressors to improve mental health during a pandemic. Further research is necessary to better understand the complex interplay between different stressors and their impact on mental health outcomes during a pandemic. Future studies should explore the potential for additional stressors, such as social isolation and caregiver burden, to interact with fear of catching COVID-19 and financial constraint. Understanding the interactions between different stressors could inform the development of more targeted interventions to support mental health during times of crisis.

Consistent with previous research [18, 31,32,33], our study found that younger age groups were at higher risk of reporting increased levels of depression during the pandemic compared to pre-pandemic levels. This is not surprising, as young adults, especially college students, undergo stressful normative changes related to their professional, financial, and social lives [34]. These stressors were intensified by COVID-related pressures, especially social isolation and financial uncertainty. While older adults are at higher risk of suffering from adverse physical effects after a COVID-19 infection, they tend to be protected from the detrimental psychological effects of COVID stressors. This may be due to the fact that older adults have had more time to develop lower stress reactivity, better emotional regulation, and stronger psychological resilience compared to young adults [35]. Therefore, they are less likely to report an increase in depression with COVID-19.

The current study revealed that females are at a greater risk of reporting an increased level of depression, partly due to increased biological, social, and cultural vulnerability. This finding may be due to females’ socially constructed caregiving role, including caring for and supporting children and the elderly, resulting in work overload during the pandemic. Greater psychological distress in females may also result from a higher percentage of the female workforce being negatively affected by COVID-19, such as in healthcare, retail, and service industries [10]. Other research suggests that females exhibit differential neurobiological responses when exposed to stressors, resulting in a higher overall rate of mental health conditions among women [36].

The study also showed that patients with pre-existing depressive symptoms were at a higher risk of reporting increased depression during COVID-19. This finding is consistent with other studies [10, 17]. Patients with a history of mental disorders may generally be more sensitive to external stressors, such as the social isolation associated with the pandemic [10]. Additionally, hospital care was affected during the pandemic, resulting in growing backlogs or delays in hospital procedures. This may have unintentionally negatively impacted care for people with pre-existing mental health conditions. This finding highlights the vulnerability and unmet needs of patients with pre-existing mental health disorders, especially in a context where access to mental health services was disrupted, as during the COVID-19 pandemic.

In this study, the association between the province of residence and increased depression during COVID-19 was examined. The results indicate that residents of Ontario were significantly more likely to report higher levels of depression during COVID-19 compared to residents of other provinces. In contrast, residents of Quebec, New Brunswick, Nova Scotia, and Prince Edward Island reported less of an increase in depression relative to other provinces. These findings are consistent with previous research that has examined psychological distress during the pandemic and demonstrated similar patterns [33]. Additionally, pre-pandemic reports have shown that Quebec residents tend to report better mental health compared to other provinces, while Ontarians generally struggle with a higher burden of mental distress [37]. It is worth noting that Ontario is one of the most populous provinces and was hit hardest by the pandemic, reporting higher case counts and deaths compared to other provinces [38]. Therefore, the higher depression levels reported by Ontario residents may be due to the greater impact of the pandemic on their daily lives. Furthermore, the pandemic, along with variations in provincial policies to control its spread, may have highlighted pre-existing variations in mental health between provinces, as has been observed with women’s mental health, as discussed previously.

This study had several strengths, including: (1) limited potential for selection bias as participants were not recruited based on their depression status; (2) the same participant rated their level of depression before and during COVID-19, providing more consistent information; and (3) the use of statistical weighting to account for the survey sampling structure. However, this study also has some limitations that should be considered when interpreting the results, including: (1) potential recall bias as participants may have over or underestimated their level of depression prior to COVID-19; (2) self-reported evaluation of depression status; and (3) being a cross-sectional study, which precludes conclusions regarding causality. Additionally, it is worth noting that psychological responses to the pandemic may have been more prevalent in the earlier stages and gradually attenuated with time for some individuals, while for others, it may sustain over longer periods, contributing to the development of persistent mental health disorders. Future longitudinal research is necessary to determine the temporal dynamics of psychological responses to the pandemic.

It is necessary for government officials to shift their mindset away from uniform approaches and recognize the varying levels of risk for different subgroups that may contribute to differences in depression and tailor their responses accordingly. Our results highlight the need for improving access to mental health services, targeted intervention, and wider depression screening during pandemics or other public health crises. Policymakers need to consider the impact of public health measures, taken to control the spread of pandemics, on Canadians’ mental wellbeing. Financial support could be provided to people who are experiencing financial hardship or loss of jobs due to the pandemic. Our findings also suggest the importance of expanding depression screening in primary care settings and providing more frequent evaluations of the needs of patients with pre-existing mental disorders. These steps can help to alleviate the significant burden of depression caused by the COVID-19 pandemic.