A physical one is often obvious, although thinking about it now, there are many that aren't. However, mental illness seems so difficult to identify as the function of identification, your brain, has the problem. I'm using a ruler to measure, but if the ruler is the wrong length I'm always wrong but I can't see that. I don't think I have any issues. My friend is going to see a therapist, which I didn't really know until recently. I'd classify it as not leaving the house enough..being dr. knowitall of course. Mostly as I feel like hiking in the hills and wilds have a very positive impact on me, and so presumably others.