Emotional support dogs are considered comfort companions. They do not perform a specific task.
There’s a saying that says “Many dogs are emotional support dogs, but most are just free lancing.”
Typically, in order to be considered an emotional support dog, a mental health professional must prescribe the dog for a patient with a diagnosed psychological or emotional disorder, such as anxiety or depression.
Airlines are no longer required to accommodate emotional support animals, but the Fair Housing Act requires “reasonable accommodations” for emotional support animals.
Note: Dogs can have their own anxieties, and sometimes clients find they have taken on a dog that barks, or is destructive in an apartment complex or college dormitory, due to separation anxiety, etc. which then exasperates their own anxiety.