Just because someone smiles doesn't mean everything's all peachy. Which is why researchers are now taking a closer look at our facial expressions and using them to teach virtual therapists how to spot mental illness, The Atlantic reports We first wrote about the technology last August , when researchers found that a virtual therapist could put clients at ease. Nicknamed Ellie, this animated therapist is someone you can talk to just like any other mental health professional — but one who has highly sophisticated cameras and MultiSense software trained right on your face. By picking up on body language subtleties (e.g. if you break eye contact) and asking the right follow-up questions (e.g. "Can you tell me more about that?"), Ellie can simulate the experience of seeing a human therapist.So, what can we learn from Ellie about how our facial expressions relate to depression? Here are some of the most fascinating tidbits the MultiSense team has found so far:For many reasons, smiling doesn't necessarily mean you're happier (for one thing, we often smile at people just because they're smiling at us). Instead, researchers found that , overall, depressed people smile just as often as non-depressed people. But the duration of each smile is much shorter in people with depression, and those individuals' smiles are deemed less "intense."Frequency of smiling matters — for women, at least. Unlike men (who frown more often if they have depression), depressed women frown less frequently than non-depressed women. So, a virtual therapist is significantly more accurate when it takes its client's gender into account. Go figure!Facial expressions are just one thing these researchers are interested in tracking. Specifically, they've found that their data is more accurate in diagnosing both depression and PTSD when it accounts for speech patterns, such as how much space a participant leaves between vowels.Apparently, your smiles say a lot more about you than you might realize. So don't let the haters force you into faking them