Yes you CAN assess a person's general health just by looking at them.    Are they standing in line with a cane, or using a wheelchair?  Are they standing up straight, good symmetry, very healthy & solid musculature?  What is their skin tone, does their face look drawn, puffy or not what a face of a person in generally good health?  What about the eyes, which are the window of the soul & often can reflect the health of a person (is it sunken, jaundice looking, etc). If someone has long term serious health problems that require weed to alleviate pain, chances are their exterior physical appearance reflects their internal health condition.  Animals who select their mates inherently know this as well.  I saw that long line of people waiting to buy weed & came to that same conclusion as SueH.  In all seriousness many looked like they were waiting to get into a dance club & had the physical stamina to wait hours standing in that line.  Many use weed for recreation & to tune out reality.