  As impact of COVID-19 pandemic winds down, both individuals and society
gradually return to pre-pandemic activities. This study aims to explore how
people's emotions have changed from the pre-pandemic during the pandemic to
post-emergency period and whether it has returned to pre-pandemic level. We
collected Reddit data in 2019 (pre-pandemic), 2020 (peak pandemic), 2021, and
2022 (late stages of pandemic, transitioning period to post-emergency period)
from subreddits in 128 universities/colleges in the U.S., and a set of
school-level characteristics. We predicted two sets of sentiments from a
pre-trained Robustly Optimized BERT pre-training approach (RoBERTa) and graph
attention network (GAT) that leverages both rich semantic and relational
information among posted messages and then applied a logistic stacking method
to obtain the final sentiment classification. After obtaining sentiment label
for each message, we used a generalized linear mixed-effects model to estimate
temporal trend in sentiment from 2019 to 2022 and how school-level factors may
affect sentiment. Compared to the year 2019, the odds of negative sentiment in
years 2020, 2021, and 2022 are 24%, 4.3%, and 10.3% higher, respectively, which
are all statistically significant(adjusted $p$<0.05). Our study findings
suggest a partial recovery in the sentiment composition in the
post-pandemic-emergency era. The results align with common expectations and
provide a detailed quantification of how sentiments have evolved from 2019 to
2022.
