I have both a psychiatric and normal one. i did them because i am totally on my own in the world, i have no one who will stand up and fight for me, so i did them just incase i need them. mine go a bit further than stating what meds i will accept, they state my allergies, all my dx's how they normally affect me, what works to alleviate symptoms, a DNR, what is to happen to my animals, and instructions not to contact family or sell my house and details of how to find my will and funeral requirements.

having all this in place gives me peace of mind that my wishes will be followed if i am unable to communicate them.