I have years ago, or rather my social worker did it for me (without my knowledge!)
I think if you can't drive due to meds you are automatically entitled to one, but it depends where you live as different councils have different rules about who gets them and why. Some councils you just have to show you have a mental illness and need to get to appointments using transport. I'd check with your council and if you have a CPN or social worker ask them to help you to fill out the application.
look up the criteria on your council web site mine its dla middle rate god knows what'll happen when it becomes pip which i suspect low rate, it helps if you've got representation
The women at the disability centre phoned up about a freedom pass they said all passes are the same the women said this isn't and described it, the reply was "thats a concessionary pass for the mentally ill"
I view that as discrimination also i can't use it on buses in brum when seeing mother, i've now got a full freedom pass