(Photograph by Deb Lindsey)

You don’t have to like your colleagues, but you shouldn’t have to fear them. Two cases of disquieting co-workers.

Reader: I work at a large office where another employee is obviously mentally ill. She has always been withdrawn and uncommunicative, not even making eye contact in the hall. Lately, she appears almost catatonic, with no natural expressions or reactions. She looks like a ghost. She has worked there for at least a decade and is now the “elephant in the room.”

How can I know that HR is addressing or assessing her problem? To what extent should it? “Had a history of mental illness” and “always kept to him-/herself” are quotes repeated in so many news stories about violent outbursts.

Karla: Maybe I’m overly protective of introverts, but I think it’s a leap from a subdued personality to “mentally ill.” I’d be more concerned about “violent outbursts” if you had mentioned red flags beyond her flat affect: manic states, threats, clashes with authority, poor performance.

Your colleague may be battling illness or depleted from caring for a sick relative. She could have a social phobia or be a victim of domestic abuse. Whatever the issue, she shouldn’t have to be a suspected threat to her co-workers for her change in personality to merit concern.

Expressing that concern can be tricky, though. Employers have to “strike a balance between being helpful and not being intrusive,” says Declan Leonard, managing partner at employment law firm Berenzweig Leonard. In particular, they must avoid “playing doctor” with off-the-cuff diagnoses such as “we think you might have depression,” which recasts the conversation — and any future actions — through the lens of the Americans With Disabilities Act. A better approach, says Leonard, is for her manager to open a dialogue that focuses on performance, including interpersonal behavior: “I notice you seem detached or distracted lately, and I’m concerned about you. Is everything all right?” And then her manager should listen, maybe with the number of the company’s employee assistance program handy.

Notice I said “her manager.” So where does that leave you, her nervous co-worker? Leonard recommends you approach the manager: “Luna seems quieter than usual lately, and it worries me. I thought I should bring it to your attention.” The manager should confirm that the matter is being or will be looked into. If not, you may want to contact HR — but your stated focus should always be Luna’s well-being.

Next week: A scary staredown.

Karla L. Miller is ready to hear your work dramas and traumas. Send your questions to wpmagazine@washpost.com. You can also find her on Twitter, @KarlaAtWork, or Facebook.

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