Author Julie Barton was 22 when she was diagnosed with an acute, and seemingly treatment-resistant, form of depression.
She tried prescription medication, psychiatry and therapy, but nothing could tame the black dog that gnawed at her very essence.
As she descended into a state of hopelessness, she decided to do "one hopeful thing". She bought a Golden Retriever puppy called Bunker. Little did she know how much solace he would provide...
"Bunker didn't ask me to tell him how I was feeling," she recalls. "He didn't need me to label my emotions, to tell him what had happened or why I was so sad. He just met me where I was.
"He met me physically, on the floor, and pressed his body into mine, licked my face, made me take deeper breaths than I had in days, made me laugh even. He had no expectations. He didn't care if I felt better. He just wanted me."
There is a quote often found on the waiting room walls of veterinary surgeons that reads: "There is no psychiatrist in the world like a puppy licking your face". It's a sentiment that resonates with Barton. She calls Bunker her "lifeline".
"That unconditional acceptance is so very freeing for someone suffering from a dire sadness," she continues. "And it's something a human can very rarely do for another human. Only an animal can consistently do this for us."
Barton's relationship with Bunker is the subject of a memoir, Dog Medicine, which was released last week.
Dublin-born healthcare assistant Ciara Morrison is one of the many people looking forward to reading it.
Morrison can relate to the story. She suffers from acute anxiety and has been attending psychiatric services since the beginning of 2012.
"Throughout the first year of being in and out of hospital, I had a little dog called Teeny and I absolutely adored her," she explains.
"She used to know when something was wrong. If she ever heard me crying, she would come running like some sort of mini superhero! When she'd reach me, she'd lick the tears off my face until I laughed and then dutifully curl up in my lap and stay there until I'd move her.
"If I was very depressed and struggling to get out of bed, she'd be there licking my face and nudging me until I moved."
These women's stories aren't unusual. Dogs are well known to promote healing. Studies show that just a few minutes of bonding with a canine can lower blood pressure, slow the heart rate and reduce shallow breathing.
However, while the therapeutic effects of dogs are the most studied and documented, there are many more animals proven to provide comfort and support.
Vlogger Melanie Murphy, who was diagnosed with generalised anxiety disorder at 19, believes that cats can help reduce stress and ease tension. And she should know - she once owned five feline friends.
"When you're stressed, hug an animal. That is the best advice I can give to the world," Melanie (pictured below) says.
Emerging research suggests that a cat's purr, like other low-frequency vocalisations in mammals, may have healing properties. It's better known as "purr therapy".
Equine-assisted therapy is another growing field. Therapeutic riding coach Sandra Schmid of Hairy Henry Therapeutic Riding (hairyhenry.com) in West Cork has many success stories.
"There's one young girl who started with me when she was eight. She'll be 11 soon. When she first came to me, she struggled with separation anxiety and panic attacks.
"She has grown hugely in confidence over the years. She still suffers from panic attacks at school and at home, but she has never had one when with me, despite two falls off the horse and a couple of other minor incidents."
While equine-assisted therapy can be an investment, there are many more forms of animal-assisted therapy for those that can't afford it.
Even the passive act of watching fish swim has been proven to reduce anxiety, while smaller, less time-consuming animals can be just as therapeutic.
Morrison has since bought two tortoises called Stomp and Brutus. "I find it so relaxing to tend to their table. It's like my own mini, indoor garden," she explains. "I spend ages arranging it and placing nice stones around, building little mounds for them to climb. It's a great way to stay present in the moment and practice mindfulness with very little effort."
She adds that those suffering with mental health issues should be mindful of the upkeep required with certain pets.
"Don't take on a complex animal that requires stringent care if you are still in an early phase of your recovery," she says. "Taking on too much could actually stress you out more. Start small."
It's a point echoed by Barton. "I caution against a severely depressed person rushing out and getting a dog, especially if they've never had a dog or didn't grow up with them.
"When I adopted Bunker, I was in a particularly rare and privileged position of having no job, no kids, two capable caretakers in my parents and no immediate financial concerns."
She also reminds that animal therapy can come from all manner of sources. "There's all kinds of medicine out there in the animal kingdom. It's merely our job to be vulnerable and open enough to see it and accept it."