The COVID-19 pandemic is a critical incident that has been accompanied by drastic and sudden changes in individuals’ daily lives and societal functioning. Beyond the mental distress tied to the uncertainty and fear of an unknown virus, the pandemic’s concomitant social distancing protocols have been suggested to pose a significant burden on individuals. The abrupt changes in individuals’ everyday lives resulting from these measures prompted early concerns about mental health and depressive symptoms in the population.
This doctoral thesis examines the impact of the COVID-19 pandemic and its accompanying distancing protocols in connection with depressive symptoms in the general adult population in Norway over a two-year period. The project spans from March 2020, ensuing the initial implementation of social distancing protocols in Norway, to March 2022, where these protocols were discontinued. The thesis encompasses three longitudinal studies that investigate depressive symptomatology during the pandemic across different levels of granularity.
Study 1 followed 4,361 adults (≥ 18 years) over the first 1.5 years of the pandemic across six longitudinal assessment waves, forming 26,166 observations. The participants were measured upon each modification of national social distancing protocols, enabling investigation of the association between these protocols and changes in depressive symptomatology over time in the same group of individuals. Societal SARS-CoV-2 infection rates were further measured to investigate how this stressor was linked to depressive symptoms. Employing a non-linear longitudinal model (Latent Change Score Model), Study 1 identified that depressive symptom levels in the adult population were associated with social distancing protocols, but unrelated to infection rates. This contrasted with observed changes in anxious symptomatology, which were more closely related to societal SARS-CoV-2 infection rates. Longer periods of sustained social distancing protocols were related to prolonged periods of heightened depressive symptoms. Increasing the stringency of social distancing protocols was associated with higher levels of depressive symptoms, while reducing the stringency and discontinuation of these protocols was associated with subsequent reductions in depressive symptomatology. This demonstrated that, on the population level, the observed increases in depressive symptoms were temporary and decreased after the termination of these protocols. When examining depressive symptom change patterns on the individual level however, Study 1 identified a smaller subgroup of adults whose mental health had deteriorated during the pandemic. These findings indicated the presence of heterogeneous responses to the pandemic across adults.
Study 2 investigated whether these individual differences could reveal subgroups of adults displaying distinct and prototypical depressive symptom change patterns during the pandemic. A Latent Change Score Mixture Model was applied to model change over time in 4,361 adults. Through the investigation of depressive symptom levels across nine assessment waves (39,259 observations) from March 2020 to March 2022, five distinct depressive symptom change profiles were identified. The majority of adults displayed either resilience to depressive symptoms (42.5%), or a temporary heightening (i.e. initial shock) in depressive symptomatology during the onset of the pandemic (13.2%). A third subgroup of individuals, predominantly with previous mental health difficulties, reported high levels of depressive symptoms that lasted from the onset throughout the pandemic period (8.5%). A fourth group of adults exhibited mild deterioration in depressive symptom levels during the pandemic (29.0%). A final subgroup of approximately 6.8% of adults displayed strong deterioration and clinically severe levels of gained symptoms occurring during the initial months of the pandemic, which was sustained over the two-year assessment period of this study. The two deteriorating subgroups of individuals did not report any signs of pre-existing psychiatric conditions and reported low levels of depressive symptoms at the beginning of the pandemic. These individuals reported a high probability of seeking psychiatric treatment by the end of the two-year study period. This indicates the potential emergence of a new subgroup of adults with severe depressive symptoms during the pandemic. Both resilient and adverse types of change patterns in depressive symptoms occurred during the first three months of the pandemic.
The risk factors related to increases in depressive symptoms levels identified across Study 1 and 2 were increased alcohol consumption during the pandemic, lower education, living alone, and belonging to an ethnic minority. The initial shock that was observed in depressive symptoms in a subgroup of adults was predicted by frequent information acquisition about the pandemic, in addition to financial and occupational concerns tied to the pandemic’s economic repercussions. An additive dose-response relationship was identified between quarantine exposure and depressive symptoms. Protective factors related to resilient response patterns during the pandemic were being in a relationship, older age, and long-term engagement in physical activity.
Study 3 aimed to extend beyond risk factors to identify psychological mechanisms that were related to increases in specific symptoms of depression during the pandemic. This study followed 1,706 Norwegian adults, each person measured daily over a 40-day period, accumulating into a total of 68,240 observations across adults. A dynamic network model (i.e. multi-level graphical vector autoregressive model) was implemented to examine the relationship between psychological mechanisms and specific symptoms of depression. The study found helplessness to be the key psychological mechanism predicting increases in depressive symptoms over time during the pandemic. Loneliness was identified as a predictor of depressed mood. The study further corroborated how depressive symptoms can amplify each other on an across-day basis during the pandemic. Lethargy and worthlessness were identified as the symptoms with the strongest impact on additional symptoms of depression (i.e. depressed mood and anhedonia, respectively), highlighting the key role of these symptoms in pushing individuals toward prolonged depressive states during the pandemic.
Overall, this doctoral thesis identified that most adults over time displayed resilience to the abrupt societal changes that accompanied the COVID-19 pandemic. Temporary fluctuations in depressive symptoms on the population level were associated with the pandemic’s social distancing protocols. However, a minority subgroup of adults exhibited severe levels of depressive symptoms which emerged during pandemic, without any signs of recovery over a two-year period. Many adults in this subgroup reported seeking psychiatric treatment. Should these trends persist, this underscores a need for careful planning and resource allocation to facilitate preparedness and avoid the potential overburdening of mental healthcare systems. The link between financial concerns and depressive symptoms suggests that the implementation of socioeconomic policies may be warranted during pandemics. Disseminating information about physical activity as a protective factor and frequent information acquisition behaviour as a risk factor could present a useful public health strategy to protect against depressive symptoms during pandemics. The first three months of the pandemic were revealed as a critical period for pandemic adaptation, representing a key time window for implementing preventive measures in future pandemics and similar periods of infectious disease. This thesis further highlights the need for a balanced approach to social distancing, considering their association with depressive symptoms in several subgroups in the population. Such a cautious approach could entail the early implementation of social bubbles and similar interventions, both permitting some degree of social interaction while mitigating infectious spread, thereby having the potential to safeguard psychological as well as physical health.