Our objective was to mine Reddit to discover long-COVID symptoms self-reported 
by users, compare symptom distributions across studies, and create a symptom 
lexicon. We retrieved posts from the /r/covidlonghaulers subreddit and extracted 
symptoms via approximate matching using an expanded meta-lexicon. We mapped the 
extracted symptoms to standard concept IDs, compared their distributions with 
those reported in recent literature and analyzed their distributions over time. 
From 42 995 posts by 4249 users, we identified 1744 users who expressed at least 
1 symptom. The most frequently reported long-COVID symptoms were mental 
health-related symptoms (55.2%), fatigue (51.2%), general ache/pain (48.4%), 
brain fog/confusion (32.8%), and dyspnea (28.9%) among users reporting at least 
1 symptom. Comparison with recent literature revealed a large variance in 
reported symptoms across studies. Temporal analysis showed several persistent 
symptoms up to 15 months after infection. The spectrum of symptoms identified 
from Reddit may provide early insights about long-COVID.