@Ælis It is an interpersonal issue (and presumably on topic here), but you may still find the answers on Workplace to be more focused on professionalism and taking into account workplace-specific details. Some of the answers here may not be as appropriate in a workplace setting or require a specific personality type or a closer relationship with coworkers. — NotThatGuy 1 min ago

The following is opinion and is just something to consider. Not wanting to answer questions about health is perfectly acceptable, but treating mental health in a special category that you "won't talk about" just continues the stigma mental health has. Consider talking about it because it should be treated like any other disease, something that effects your ability to do work that requires professional help. — Sam 2 mins ago