A new study in Canada found that when people report their own health conditions, it doesn't always match what healthcare professionals think they have. In fact, for some conditions like depression and PTSD, people reported having them less often than doctors said they did. But for other conditions, like hepatitis C, people's self-reported reports matched what the doctors said they had. This study is important because it shows that people's own reports of their health can be unreliable, and healthcare professionals should be careful when relying on those reports.