The association between worldwide COVID-19 vaccination and mental health has been largely unexplored by means of infodemiological studies.
ObjectiveTo explore how global public interest in different mental health topics changed between the pre-vaccination pandemic stage and the different periods of the COVID-19 vaccination campaign.
MethodsIn this study were examined the relative search volume (RSV) in Google Trends for ‘anxiety’, ‘depression’, ‘stress’, and ‘suicide’ between 1 March 2020 and 1 January 2023. The RSV for each term was compared with respect to 4 periods: the pre-vaccination pandemic stage; the period from initiation of vaccination until 50% of the population was fully vaccinated (FV); the period from 50% FV to 60% FV; and the period after 60% FV.
ResultsA significant lower mean RSV on anxiety, depression, and suicide was found once 60% of the world population had been FV compared to different previous vaccination periods and with the pre-vaccination pandemic stage.
ConclusionsThere seems to be less need for information worldwide on anxiety, depression, and suicide topics once 60% of the population is FV against COVID-19. Overcoming this vaccination milestone may have had a positive impact on public interest in specific mental health issues.
La asociación entre la vacunación mundial contra el COVID-19 y la salud mental ha sido en gran medida inexplorada por medio de estudios infodemiológicos.
ObjetivoExplorar cómo cambió el interés público mundial en diferentes temas de salud mental entre la etapa de pandemia previa a la vacunación y diferentes períodos de la campaña de vacunación contra el COVID-19.
MétodosEn este estudio se examinó el volumen relativo de búsqueda (VRB) en Google Trends para los términos «anxiety», «depression», «stress» y «suicide» entre el 1 de marzo de 2020 y el 1 de enero de 2023. Se comparó el VRB para cada término con respecto a 4 períodos: la etapa de pandemia previa a la vacunación; el período desde el inicio de la vacunación hasta que el 50% de la población estuvo completamente vacunada (CV); el período del 50% al 60% de la población CV; y el período posterior al 60% de población mundial CV.
ResultadosSe encontró un VRB medio significativamente más bajo en ansiedad, depresión y suicidio una vez que el 60% de la población mundial había sido CV en comparación con diferentes períodos de vacunación anteriores y con la etapa pandémica previa a la vacunación.
ConclusionesParece haber menos necesidad de información a nivel mundial sobre temas de ansiedad, depresión y suicido una vez que el 60% de la población está CV contra COVID-19. Superar este hito de vacunación puede haber tenido un impacto positivo en el interés público en temas específicos de salud mental.
Infodemiology is a field within health informatics in which Internet data are used to analyse diseases and to determine social behaviour in relation to various health topics1,2. Different health assessment studies based on web data usage have shown that changes in Internet information search patterns can be indicators of changes in the public's health. They can be used to evaluate, monitor, and predict outbreaks of infectious diseases and to recognise the public's health information requirements in real time.2–4
The effect of global vaccination against SARS-CoV-2 on mental health has scarcely been explored through infodemiological studies. Worldwide studies have focused on analysing the impact the COVID-19 vaccine has had on the volume of Internet searches on topics related to fear and economic anxiety,5 and also on examining the relationship between those fully vaccinated, and web searches on anxiety and depression topics6.
These investigations were conducted only taking into account the pandemic period between 2020 and 2021,5,6 and they did not include web searches carried out using terms such as ‘suicide’ or ‘stress’, which are topics that were usually analysed in previous studies that explored the pandemic's impact on public interest in mental health.7–9 General interest research studies on various mental health topics (in addition to anxiety and depression) are needed in relation to different SARS-CoV-2 vaccination milestones during the period between 2020 and 2023. Against this backdrop, the objective of this paper was to examine how public interest changed worldwide regarding different mental health topics between the pandemic phase prior to the start of immunisation and during different periods of the COVID-19 vaccination campaign.
MethodsThe information on the different COVID-19 vaccination milestone achievement dates and the fully vaccinated (FV) global population percentages (i.e., with 2 doses of the SARS-CoV-2 vaccine) was obtained from the OurWorld in Data vaccination database.10,11
Web search trends on different mental health terms (MHTs) were identified using the Google Trends (GT) tool.12 This online resource provides a relative search volume (RSV) index for different keywords within a specific search category, geographic area, and time period. The MHTs used in this study were ‘anxiety’, ‘depression’, ‘stress’, and ‘suicide’. The searches were carried out worldwide, in all categories of web queries (science, health, news, entertainment, education, society, and literature) and the terms were written in English.
The weekly RSV in GT for the indicated MHTs was collected in the 148 weeks from 1 March 2020 to 1 January 2023 and the frequency of web searches for these MHTs was compared in 4 periods: period 1: stage pre-vaccination pandemic (1 March–12 December 2020); period 2: phase from the start of the COVID-19 vaccination campaign until 50% of the world's population was FV (13 December 2020–10 January 2022); period 3: period from reaching 50% of the FV world population to 60% of the FV world population (11 January–23 June 2022); period 4: stage after reaching 60% of the world population FV (24 June 2022–1 January 2023).
Subsequently, descriptive statistics (mean and standard deviation) of the RSV were calculated in each of the periods and the assumptions of normality and homoscedasticity of the measurements in them were evaluated using the Kolmogorov–Smirnov and Levene tests. To determine if there were differences between the different vaccination stages studied, a one-way analysis of variance (ANOVA) was applied (time period), or the Kruskal–Wallis test if any of the parametric assumptions were not met, and the Bonferroni correction post hoc test was used for multiple comparisons. The analyses performed were completed with the Eta square test (η2) as a measure of effect size. Statistical analyses were performed using SPSS 25.0.
ResultsIn the total number of weeks studied, anxiety was the term of greatest interest (RSV=25.68±1.57), followed by stress (RSV=25.01±2.35), depression (RSV=21.49±2.37), and suicide (RSV=19.56±9.96).
A significantly lower mean volume of Internet searches for anxiety, depression, and suicide was found once 60% of the global population had been VF compared to previous vaccination periods and to the pre-vaccination pandemic stage (Table 1). Moreover, a lower RSV was found for the terms ‘depression’ and ‘suicide’ during periods 2 and 3 compared to the pandemic period prior to the start of vaccination. Regarding the term ‘stress’, a significantly lower RSV was found during period 4 than during period 3 (Table 1). In contrast, a higher average volume of Internet searches about stress was found in period 3 compared to the pre-vaccination stage and period 2. Similarly, a higher RSV was found for the term ‘depression’ in period 3 compared to period 2 (Table 1).
Comparison of the relative search volumes in Google Trends for the terms ‘anxiety’, ‘depression’, ‘stress’, and ‘suicide’ in the periods studied from the beginning of the pandemic until more than 60% of the world's population was completely vaccinated against COVID-19.
| MHT | P1 (n=41) RSV | P2 (n=57) RSV | P3 (n=23) RSV | P4 (n=27) RSV | Statistic | η2 | Post hoc differences |
|---|---|---|---|---|---|---|---|
| Mean (SD) | Mean (SD) | Mean (SD) | Mean (SD) | ||||
| Anxiety | 25.78 (1.49) | 25.88 (1.37) | 26.13 (1.63) | 24.70 (1.43) | H=14.64⁎⁎ | 0.09 | P4<P1⁎⁎P4<P2⁎⁎⁎P4<P3⁎⁎ |
| Depression | 23.44 (2.02) | 20.28 (1.54) | 22.83 (2.05) | 19.93 (1.88) | F=34.42⁎⁎⁎ | 0.41 | P4<P1⁎⁎⁎P4<P3⁎⁎⁎P2<P1⁎⁎⁎P3>P2⁎⁎⁎ |
| Stress | 24.32 (1.75) | 24.58 (2.07) | 27.78 (2.39) | 24.59 (2.09) | F=16.85⁎⁎⁎ | 0.26 | P4<P3⁎⁎⁎P3>P2⁎⁎⁎P3>P1⁎⁎⁎ |
| Suicide | 19.54 (5.58) | 22.14 (14.86) | 17.39 (1.72) | 16.00 (1.79) | H=30.10⁎⁎⁎ | 0.05 | P4<P1⁎⁎⁎P4<P2⁎⁎⁎P4<P3⁎⁎P3<P1⁎ |
F=F-ANOVA; H=Kruskal–Wallis test; MHT=mental health related terms; n=number of weeks included in each period; P1=pandemic period prior to vaccination; P2=stage from the beginning of vaccination until 50% of the population was FV; P3=period when 50%–60% of the population was FV; P4=phase after 60% of the population was FV; RSV=relative search volume; *p<.05; **p<.01; ***p<.001.
These GT-based findings showed that, once 60% of the world's population had been fully vaccinated, public interest in different mental health topics decreased compared to the pre-vaccination pandemic stage and to different previous vaccination periods analysed.
Public interest in anxiety, depression, and suicide on the Internet was specifically lower once 60% of the world's population was FV compared to various previous vaccination and pre-vaccination stages examined. Given that a reduction in the perceived risk of COVID-19 and its consequences (hospitalisation, death, etc.) was associated with vaccination against SARS-CoV-2,13,14 the public need for information on anxiety, depression, and suicide dropped, which could indicate a reduction in fear regarding COVID-19 and its global consequences. Globally, this positive change could be particularly important when vaccination rates exceeded 60%. These findings align with a previous infodemiological study, which found a negative correlation between public concerns regarding emotional distress and the number of people vaccinated.6 They also align with other research studies, such as that carried out in the United States, which found a lower level of anxiety and worry in the general population associated with the increase in the number of FV individuals.15
In the case of stress, the variation in web searches on this topic was somewhat different. We only found that public interest on the Internet in topics related to stress was lower once 60% of the population was FV compared to the period in which 50%–60% were FV. These findings are in line with the results from different international studies on vaccination against SARS-CoV-2 and mental health.6,15
Several limitations should be highlighted in our study. First, the information obtained through GT does not represent a random sample of the world population, since there could be groups that are interested in mental health issues, but who do not have access to the Internet or who use different terms than those analysed to carry out web searches. Second, the search volume data collected by GT is relative, not absolute, and provides us with information only on those users who use Google as a web search engine. Third, there is no standard procedure for data collection using GT, and the selected terms and their spelling may affect the results.
Finally, we should consider that web searches on mental health could be conditioned by other pandemic-associated factors not included in this study, such as non-pharmacological measures (e.g., the use of masks), circulating COVID-19 variants or mobility restrictions, which are more heterogeneous variables than the dynamics and pace of global vaccination.
To conclude, there appears to be less need for information on anxiety, depression, and suicide topics once 60% of the population has been fully vaccinated against COVID-19. Achieving this vaccination milestone may have had a positive impact on mental health among the general population globally, as reflected by fewer Internet searches for the psychopathological processes mentioned above.
FundingThis study was partially funded by the Universidad Internacional de La Rioja (UNIR, http://www.unir.net) within the framework of the RETOS-UNIR Research Project Strategy (2018–2024).
Authorship contributionAll the authors of this study have contributed intellectually to its development (in the conceptualisation, design, analysis and initial writing), and have participated in the review and editing of the final version of the submitted manuscript.