You can't talk about someone being depressed at work. Mental health is a touchy subject. If someone looks depressed or doesn't show up to work for several days in a row, it's better to leave the issue to the professionals.

Those are all false statements about workplace mental health. The truth is, if someone looks depressed and lethargic, they sleep in late and don't laugh at any jokes, and seem to be just pushing themselves to do anything at work, it's not a bad idea to ask a question.

In a recent talk at the Roe Green Junior School in London, royal mom Kate Middleton mentioned how the first step in dealing with mental health is to have a conversation. It's true. Sometimes, just one question--at school, in your own family, or at work--can help someone realize they need to take action, to seek professional help.

Few of us are experts in the field. But we are in the field.

All of those doctors and counselors who know exactly what to say and how to say it, to probe and provide the right level of comfort and support--they are in offices at a clinic across town. They can't be at your startup or on your sales team.

"We know that mental health is an issue for us all--children and parents, young and old, men and women--of all backgrounds and of all circumstances," she said in the speech. "What we have seen first-hand is that the simple act of having a conversation about mental health--that initial breaking of the silence--can make a real difference," said Middleton. "But, as you here today know: starting a conversation is just that--it's a start."

How do you even muster the nerve to ask?

For some of us, it's easier. Extroverts in particular can be more blunt about this topic, and they have a way of almost turning it into a topic of conversation. It's more awkward for introverts. Yet, it could be a simple matter of taking a coworker out for coffee. You don't have to ask the question "are you depressed?" but instead start asking about life, about how work is going, about motivations, desires, and recent successes.

The truth is, you will know within a matter of minutes if there is a serious problem. The person won't look you in the eye, or they will seem evasive, or they'll come up with excuses. When you see that there are signs of mental illness, it might not be your job to suggest what to do or how to resolve it, but it is perfectly acceptable to listen and be a friend. It's perfectly fine to start the conversation, even if you don't know where to take it or how to come up with an action plan (few of us know how to do that).

As Middleton said, in describing how she plans to launch a website on the topic and expressing a strategy that works: "I see time and time again that there is so much to be gained from talking of mental health and taking the mental health of our children as seriously as we do their physical health. When we intervene early in life, we help avoid problems that are much more challenging to address in adulthood."

Will you look around? If someone is hurting, don't wait until they go to a mental health professional. Don't be blunt or rude. Just listen, and be a friend.