The short answer
"Slack anxiety" is the stress and overthinking that builds up around workplace messaging apps — rereading a message before sending it, feeling a spike of dread when a notification appears, and reading tone into a coworker's one-line reply that probably isn't there. It's not a clinical term, but the underlying pattern is well documented and surprisingly common.
How common this actually is
Multiple surveys converge on a similar picture: close to half of workers report overthinking the messages they send, and a majority say workplace messaging apps contribute meaningfully to their day-to-day stress. One frequently cited figure puts the share of workers who feel some anxiety opening their Slack inbox above half. The specific numbers vary by survey, but the direction is consistent — asynchronous work messaging has become a real, measurable source of low-grade dread for a lot of people, not just an inconvenience.
Why messaging apps specifically produce this
Part of the mechanism is what researchers call the "email urgency bias" — the tendency for the person receiving a message to overestimate how quickly a reply is expected, even when the sender had no such expectation. That mismatch creates pressure on both ends: senders wonder if their message read as too curt or too demanding, and recipients feel obligated to respond faster than the situation actually requires.
The always-on nature of the format compounds this. A phone call ends. A Slack channel doesn't — it's there to be reread, checked, and worried about long after the workday's natural stopping point.
Where it shows up most
The pattern tends to concentrate around ambiguous, short messages from someone with authority over your work — a manager's "can we talk later?" or a one-word reply to something you spent time drafting. The lack of tone in a short message does a lot of the damage: the same three words read as neutral from a peer and as ominous from a manager.
Want to see this pattern in your own thinking, not just in the research?
What actually helps
The research on ambiguous-message interpretation generally suggests that the negative reading of a short or delayed message usually comes from the reader's anxiety, not from anything wrong with the message itself. Waiting to interpret a message until there's actual information, rather than filling the gap with the worst available guess, is the theoretically sound advice — and also very hard to do in the moment.
What tends to be more practical is noticing when the overthinking starts, rather than trying to reason your way out of it while it's happening. Marking the moment — this is the spiral, it's about a work message, it's happening now — creates a small amount of distance without requiring you to solve the underlying uncertainty on the spot. Over time, that record shows how often the dreaded interpretation turned out to be right, which for most people is far less often than the anxiety in the moment suggests.