Animals are increasingly prescribed as a way to help people with mental illness in the United States. What’s more, new research shows that these four-legged companions can help their “patients” function in their day-to-day lives, The Wall Street Journal reports.

So, how exactly can animals help treat psychological disorders?

One review involving children with autism spectrum disorders, published in the Society for Companion Animal Studies Journal in 2009, suggested that trained service animals can help facilitate daily routines, encourage social interactions and reduce behavioral outbursts in these children.

In addition, certain dogs can be trained to detect changes in body language—for example, when someone with post-traumatic stress disorder (PTSD) experiences a flashback, or when patients with dissociative disorders (such as schizophrenia) or anxiety attacks suffer a similar disconnect with reality. Simple touches and nudges from an animal companion can help remind owners where they are and help them remain calm through episodes.

Studies have also shown that an animal’s presence can actually induce neurochemical changes in the brain. For example, animals can trigger an increase in oxytocin, a hormone thought to improve a person’s social reactions.

This is why the use of emotional-support animals, or ESAs, are also on the rise in the mental illness community. Many of these animals are usually household pets—cats, miniature horses and even chinchillas—that require no special training. What’s more, they can be taken out in public much like highly trained pets.

Some depression and anxiety patients have reported being able to reduce their medication as a result of having an ESA. Therapists have also reported using animals to help comfort and cheer up patients undergoing treatment in psychiatric hospitals.

But some animal experts warn against the hype. The increase in the number and variety of four-legged helpers could hurt the service-animal community if mental health professionals aren’t careful with their designations.

“I have a great deal of concern about people abusing the categories [in order to take their pets] into restaurants and particularly in airplanes,” said Mary Burch, director of the American Kennel Club. “People with disabilities have struggled for public access rights for decades…and they may lose them if we abuse the system.”

Burch’s worries are compounded by the fact that there is no official national certification or registration program for assistive animals in the United States. Many times, getting an ESA designation for an animal is as easy as getting a psychologist’s note.

Animals can also help people living with medical issues such as HIV/AIDS better manage their conditions. Click here for more information.