Background
For over two years, the global society has experienced multiple waves of COVID-19 infections since its initial outbreak with new variants of concern. The Omicron variant, despite its possibly lower case fatality, has raised serious public health concerns owing to its higher transmissibility and lower vaccine efficiency [
1‐
3]. Notably, the Omicron variant had emerged at a time of prolonged COVID-19 stress [
4,
5]. Whether individuals will adapt and become acclimatised to pandemic lockdowns, or rather become sensitised amid the ongoing fluctuations of COVID-19, becomes an ever-important question.
Studies across countries have raised concerns over the mental health impacts of COVID-19 on the general population, such as increased levels of depressive and anxiety symptoms, as well as psychological distress [
5‐
9]. Of note, the increase in mental distress in relation to COVID-19 appeared most pronounced among young people [
6,
10]. Few studies, however, have yet examined factors that can potentially be modified during lockdowns to prevent the negative mental health impacts of COVID-19 [
11].
Based on observations from earlier studies, the World Health Organization (WHO) has published several reports to consolidate existing findings on the impact of COVID-19 as a guide for further research [
12‐
14]. The barriers to access to traditional mental health services had also been also highlighted, together with suggestions on approaches that may be adopted during this period, such as mental health helplines, outreach services, teletherapy, as well as self-help techniques [
12‐
14].
Specifically, maintaining regular physical activity and staying connected with others (e.g., via phone or online), while minimising the reading of distress-inducing pandemic news, have been raised to be helpful strategies in promoting mental well-being during COVID-19 [
13]. Indeed, the mental health benefits of regular physical activity (e.g., maintaining vigorous-intensity aerobic and muscle-strengthening activities at least three days a week for adolescents [
15]) have been shown in prior work [
16‐
19]. Alongside physical activity, with the growing reliance on digital devices today, smartphones have become a convenient means for young people to maintain social relationships and connections with their peers. Nevertheless, unmonitored and prolonged uses of smartphones can increase the risk of smartphone overuse (also referred to as smartphone addiction and compulsive or excessive smartphone use), which has been associated with symptoms of depression, anxiety, and psychological distress [
20‐
23]. A recent study in an epidemiological sample of young people in Hong Kong has further demonstrated the longitudinal impact of smartphone overuse on severe depressive symptoms and functioning for up to 1 year [
24].
Notably, several initial studies have reported significant increases both in sedentary behaviours [
25,
26] and smartphone use and overuse [
27,
28] in young people since the pandemic. Given that both these factors are modifiable (i.e., may be targets of interventions) and are generally less stigmatising, a more in-depth study into how these factors may together contribute to changes in mental health amid the Omicron lockdown period may offer new insights into the design of more effective and youth-friendly interventions for young people.
Existing evidence in the literature, however, is mostly cross-sectional, with data collected during the initial outbreak of the pandemic; the investigation of
changes in distress over time as new waves of infection emerge has seldom been reported. Among the several longitudinal studies available, increased levels of mental distress and psychiatric symptoms have been reported during the early months of COVID-19 [
6,
10,
29,
30]. For instance, a representative household-based longitudinal study in the United Kingdom found a significant increase both in the prevalence of severe psychological distress (from 18.9 to 27.3%) and mean levels of distress (from 11.5 to 12.6) compared to the pre-COVID period (2018–2019) [
6]. Interestingly, several studies have in contrast observed a gradual decline in distress across waves of COVID-19 [
31,
32], which have been taken to suggest a potential “habituation” effect. However, to the best of our knowledge, all such studies had been conducted before the Omicron outbreak [
6,
10,
29]. With the distinct profile of the Omicron variant, whether mental distress of the population can be further aggravated after nearly two years of protracted COVID-19 remains to be explored.
Compared to other populations, the COVID-19 situation had generally been well-contained in Hong Kong. This was until the surge of the Omicron variant in December 2021, which resulted in the most severe wave of infection thus far [
33,
34]. By March 2022, the 7-day average of new death rates related to COVID-19 had reached one of the highest in the world [
35,
36]. While restrictions began to be gradually lifted in other countries, the local government has implemented some of the most restrictive lockdown measures to date [
34], including city-wide dine-in restrictions, school lockdowns, work-from-home policies, strict travel restrictions (e.g., flight bans), as well as compulsory COVID-19 testing and compulsory quarantine at designated centres. The high population density and limited living space in Hong Kong make such large-scale lockdowns considerably more difficult to cope with [
37,
38]. The unprecedented outbreak of this wave of COVID-19 not only brought about immense disruptions to the everyday lives of the population, but also an immense strain on the public health system and the economy [
34,
39,
40].
Of note, before the advent of COVID-19 in early 2020 in Hong Kong, the population has already experienced months of large-scale social unrest from June 2019, with city-wide protests evolving into police-civilian confrontations involving the use of tear gas, bean bag rounds, and rubber bullets [
41,
42]. Arrests in connection with the social unrest have in fact been made throughout different waves of COVID-19, including the period of the Omicron outbreak in 2022 [
43,
44]. Local data have shown that these two types of population-level stressors (social unrest and pandemic-related) can interact with personal stressors to increase depressive and PTSD symptoms, particularly in young people [
45,
46]. A cross-cultural study has also observed disproportionately higher rates of suicidal ideation among young adults during COVID-19 in Hong Kong compared to other Asian and Western countries (e.g., the Philippines, Canada, United States, United Kingdom, New Zealand, Belgium, and Switzerland), which has been attributed to the cumulative effects of the social unrest and COVID-19 [
47]. Any further increase in mental distress since the surge of the Omicron variant would therefore suggest its potential to inflict further stress in a population where distress and tension are already rife.
In view of gaps in the current literature, we conducted a 6-month longitudinal study to examine changes in psychological distress among young people from an ongoing epidemiological study before and during the fifth wave of COVID-19 and the potential factors that may contribute to such changes. We hypothesised that young people would show significantly increased distress symptoms and perceived stress during this wave of the Omicron outbreak. We also anticipated a significant increase in smartphone overuse behaviours and reduction in days of vigorous physical activity during this period, which may both additively and interactively contribute to the increased levels of distress observed among these young people.
Discussion
To the best of our knowledge, this was among the first study to examine changes in mental health before and during the surge of the Omicron outbreak amid nearly two years of protracted COVID-19. We found that the emergence of the Omicron variant had contributed to a further increase in distress among young people on top of the prolonged pandemic. Notably, this elevation in distress was related to increased smartphone overuse and reduced physical activity not only in an additive but also multiplicative manner. Our findings highlighted the need to consider strategies to mitigate the consequences of similar public health crises and lockdowns in the future both in terms of mental health interventions and policy design.
The current work added to the literature in the discussion of whether mental health in young people will show patterns of adaptation to pandemic lockdowns or that their symptoms can become further aggravated as a new wave of COVID-19 emerges. In addition to examining changes in mental distress due to the Omicron outbreak, we were also interested in identifying potentially modifiable factors that may be involved in the process. We found that two important factors, namely smartphone overuse and reduced physical activity, had also been exacerbated and contributed to the elevated distress observed during the Omicron lockdown.
Particularly during lockdown periods where in-person activities and social contacts are restricted, it is acknowledged that smartphones can offer a convenient platform for such communications, the gratification of various needs, as well as coping with daily life stress [
67,
68]. However, while frequent uses of smartphones may not necessarily be problematic, smartphone overuse can have significant impacts on mental health (also reported before COVID-19 [
69,
70]) and can further contribute to poorer psychosocial functioning and both academic and work performance [
24,
71]. There had also been suggestions that an increased dependence on smartphone use during COVID-19 can further perpetuate pandemic-related fears and distress [
72]. The repeated cycles of news reading can possibly trigger a state of “event-based rumination” (i.e., repetitive thoughts about an external event), which has been shown to be associated with increased psychopathological symptoms amid large-scale population-level stress [
73‐
75].
Meanwhile, although reduced physical activity may be understandable in the context of COVID-19, the impact that extended periods of lockdown restrictions has on mental health is of concern. Importantly, our previous study using the experience sampling method has found that engagement in active leisure activities can have protective effects against the impact of restrictive COVID-19 lockdown measures on momentary negative affect [
37]. Offering suggestions to young people for maintaining physical activity that can be engaged in at home would be helpful (e.g., rope jumping, fast dancing or aerobic dancing, and even martial arts, are some examples of vigorous-intensity physical activities [
76]).
Overall, supporting young people in the healthy use of smartphones and maintaining physical activity during COVID-19 is important. While few studies to date have systematically examined the effectiveness of interventions targeting smartphone overuse, a recent systematic review noted that a combination of psychological and behavioural interventions – particularly exercise interventions – may be optimal [
77]. Together with our findings suggesting significant interactions between increased smartphone overuse (both compulsive use and its functional impacts) and reduced physical activity, incorporating exercise interventions in psychological interventions (whether delivered offline or online) may be further explored not only for maintaining physical activity, but also for preventing the worsening of smartphone overuse and improving mental health outcomes.
In the interpretation of findings of this study, we also note that some studies have reported patterns of habituation towards COVID-19 prior to the Omicron outbreak. For instance, findings from a previous local study based on data from an online text-based counselling service (N = 60,775) suggested signs of adaption and improved resilience in community members across four waves of COVID-19 from January 2019 to January 2021 [
31]. Another longitudinal study in the United Kingdom has also reported a trend of reduced depressive and anxiety symptoms across the first 20 weeks of initial COVID-19 lockdown [
32]. As with the majority of pandemic-related research, however, these studies had only covered the initial periods of COVID-19. Our current observations suggested a hitherto unanticipated effect: that after nearly 24 months of COVID-19, the Omicron surge was still able to trigger a significant aggravation in mental distress. This observation may at least partly be the result of fatigue following an extended period of COVID-19. The different nature of the Omicron variant (e.g., rapid spread to a large proportion of the population, extensive lockdowns in some areas) might also have played a role. These considerations highlighted the need for continued monitoring of the trajectory of youth mental health in the population across periods of COVID-19, as well as in the post-COVID period.
In addition, we did not find changes in resilience and the frequency of stressor exposure from before to during the fifth wave of COVID-19 in this sample. One of the reasons may owe to the assessment of resilience as a general trait (e.g., able to “adapt to change” and “bounce back”), which may be less susceptible to change as compared to adaptation in relation to COVID-19 or towards more severe or traumatic events. The two-year period of COVID-19 prior to the Omicron outbreak may also have equipped the population in adapting to the pandemic. Indeed, more recent studies have emphasised resilience not as the absence of psychopathology, but rather a dynamic and context-dependent process influenced by interdependent systems of developmental, neurobiological, psychological, and environmental factors [
78,
79]. Identifying whether subgroups of individuals may be resilient (or more vulnerable) to the impact of COVID-19 lockdowns may facilitate the identification of young people at greater mental health risks. In addition, while an “others” option was provided in the LEC for assessing personal stressors, the stressful events covered in the LEC may be less sensitive to everyday life stressors, which may be more common during COVID-19 lockdowns. Examining the impact of pandemic-related stressors, as well as how their experiences might have differed from earlier waves of the COVID-19, may be helpful for designing more specific and context-relevant interventions.
Strengths and limitations
In contrast to existing longitudinal and cross-sectional studies conducted during the initial phases of COVID-19, the current study provided evidence to document the mental health impacts of the Omicron outbreak. With the use of a longitudinal design, the current investigation offered insights into whether distress levels could be further exacerbated in the context of protracted periods of population stress. We also examined the potential contribution of smartphone overuse and reduced physical activity – both of which are modifiable and less stigmatising – to elevated distress in young people. The observation that these two factors can potentiate the effect of one another to affect mental health outcomes, even after accounting for a wide range of potential confounding factors, suggested the potential importance of considering their roles in future interventions.
Nonetheless, we also acknowledge some limitations in the study. While the K6 is a widely validated measure and has shown to be valid in predicting risk for psychiatric disorders, it cannot replace clinical diagnosis. Our current findings should be taken as a reference for the
change in those meeting the threshold of moderate-to-severe distress and distress severity instead of prevalence data. Due to the need for timely data collection, the use of simple self-administered measures is a common practice for tracking the differences in mental health before and since the outbreak of COVID-19 [
6,
10,
29,
30]. Studies that aim to establish changes in the prevalence of diagnosable conditions may combine both self-administered and clinician-rated data in the future. Despite the satisfactory follow-up rate and similar profiles of this sample and the Hong Kong population in terms of housing type and household geographic district, our sample was comprised of slightly older and female participants. If longitudinal data before and during later waves of COVID-19 were available from other studies, it would be ideal to test the current observations in other settings and populations to determine their generalisability.
In addition, brief measures indeed can be valid measures of specific phenomena and have the benefit of simple administration, which are particularly beneficial when working with young people and in time-limited settings [
49,
80]. Nonetheless, other related symptoms or subdomains of a phenomenon could not be fully captured, which can possibly provide additional information for specific intervention planning. Our single-item measures of smartphone overuse were not intended to determine clinical levels of smartphone addiction but rather to capture two key aspects of the phenomenon, namely compulsion and its impact on social and occupational functioning. It would be worthwhile to further examine whether other symptoms of smartphone overuse, such as tolerance and withdrawal, would also show similar patterns of associations. Lastly, while we focused on vigorous physical activity in this study, capturing physical activities also at light and moderate levels in the future may be helpful for determining the level of physical activity most beneficial for mental health in young people.
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