When the World Health Organisation announced in the 1980s that companion animals "bring immense benefits to their owners and to society", they were simply confirming what every pet owner already knew. 

In one paper on the subject, Sam Ahmedzai, Professor of Palliative Medicine at Sheffield University, said that there was data that suggested that the company of a pet could help to "boost the immune system, relieve pain and generate a sense of wellbeing". Pet ownership, it appears, can add something important to the emotional underpinning of physical good health.

Although there is a need for more studies, particularly of the sort that June McNicholas, a health psychologist at Warwick University, says will "meet the gold standards for medical research", the anecdotal evidence that animals are good for us is mounting all the time. So much so, in fact, that companion animals (dogs, cats, rabbits) are now being used to bring a new quality to the lives of people who, either through illness or through circumstance, find themselves isolated, lonely or at the margins of society.

Animal treatment

The idea that a pet can be a therapeutic boon to both the spirit and the body is not a new one. It was actually explored as long ago as the 18th century by a philanthropic British tea merchant called William Tuke. Appalled at the way in which mentally ill people were being treated by the authorities, Tuke set up a special retreat in York. As part of the daily restorative regime in Tuke's haven, patients were actively encouraged to care for rabbits and chickens.

Today the field of animal-assisted therapy, as it is called, is rather more advanced. This is evidenced, for example, by the work of Pets As Therapy (PAT), an organisation set up in 1983 to provide long-stay hospital patients and residents in nursing homes with regular visits from dogs and cats.

The animals - all vetted for their amiable temperaments and their spotless fur - are taken not just to hospital wards and homes but also to day care centres and special needs schools. During the visit, patients, residents and pupils have the opportunity to touch, stroke, feed and play with the animals.

A welcome visit

Even for adults, hospitals can be daunting places. But if you're a child and you're very unwell and you're faced with an endless daily routine of treatment, it's easy to feel alone, and easier still to withdraw into yourself. The arrival of a PAT pet on the ward, however, can make a transformation. Suddenly the focus is all on the dog or cat. The barriers that the children have built up to protect themselves from the world dissolve when presented with a shaggy coat to ruffle or a cat to tickle. Silent patients can suddenly open up or gradually explore conversation.

Through the pets, the children feel able to reach out to life beyond the claustrophobic clinical environment of the ward. More importantly, holding or feeding a pet allows the child to reverse the oppressive routines of the hospital: rather than endlessly receiving care, for a moment or two they can offer it instead.

The treatment isn't purely psychological either. Walking a dog along the physiotherapy unit can do marvels in helping a patient rehabilitate under-used muscles. And the joys of a visit are not limited to the children's wing. The adult wards are just as popular a destination.

A number of hospitals also use pets at precise moments in the treatment cycle, as a way of calming anxious patients. A case in point is Emma, a little girl suffering from juvenile chronic rheumatoid arthritis, a debilitating condition that entails regular visits to hospital. Especially dreaded by Emma were the injections she needed to combat the arthritis.

Nothing could ease her fear or apprehension until one day she was introduced to Katie, a chocolate-coloured PAT poodle. Now Emma receives her injections without a tear, so long as Katie is there to be stroked and touched. What once occupied 45 traumatic minutes is now over in peaceful seconds.

Caring for people in care

For older people, one of the wrenches of going to live in a residential home is that they often have to forfeit the pleasures and the companionship of a pet. The unconditional loyalty of a dog or cat can be an anchor for many older pet owners. And having to relinquish a dog or cat, perhaps after a lifetime of pet ownership, can be traumatic.

In an effort to examine the role that pets can play in providing a sense of emotional continuity in people's lives, a team from the University of St Louis in the US carried out a research programme on the effects that regular visits by companion animals had on the residents at a nursing home in the city. A dog was brought to the home once a week for six weeks. People were able to stroke, groom and walk with the animal, but they were not allowed to hold a conversation with the dog's handler.

Astonishingly, a relationship of just half an hour per week with the dog was enough for most of the residents who took part in the study to report that they felt less isolated and much more confident as a result. Not only did the dog become a centre of attention - it got people talking to each other as well.

William Banks, the St Louis professor who ran the study, said: "It's not that the animals have magic vibes coming out of them, it's a quality of life issue. For the residents, spending time with the dog helped transform the nursing home into a home."

The rules on pet ownership in residential homes in the UK tend to be rather uneven although many homes, realising the liberating effects that animal companionship can have, now allow pets as permanent co-residents. Where there are difficulties over arranging this, organisations like PAT attempt to fill the gap.