Service Dog: Psychiatric Service Dog (PSDs)
Job: To assist their handler with a psychiatric disability such as anxiety, depression or PTSD via specific, trained tasks.
Handler: Can vary widely in presentation but often appears to not have a disability. Often cited as having an “invisible” disability.
Gear: No special gear required.
Notes: Psychiatric Service Dogs are protected under the same federal laws that protect other Service Dogs. They must be given the exact same treatment and access rights. Note: Emotional Support Animals (ESAs) and Therapy Dogs are NOT the same as Psychiatric Service Dogs and are not covered under the ADA, and nor do they have any public access whatsoever.
excerpt taken from http://www.anythingpawsable.com/types-of-service-dogs