Asthma sufferers who also live with anxiety or depression are more prone to asthma attacks, a visiting expert says.
Dr Peter Gibson, a respiratory specialist at John Hunter Hospital in Newcastle, New South Wales, has been studying the "psycho-social factors" surrounding the illness.
"What it refers to is 'do you feel you're in control or have the skills and the confidence to manage your illness? Or is the illness managing you?'"
He and other researchers have found there were important relationships between the perceived control of asthma and other outcomes, such as quality of life. The less control people felt they had, the more prone they were to attacks.
This phenomenon had been seen in people suffering anxiety and depression, Dr Gibson said.
However, researchers did not yet know why this was the case.
"But it's clearly consistent, and the size of the effect is what makes it important."
There was a field of research called neuro-immunology - about how the brain interacts with the immune system and how they can modify each other, he said.
"That could explain the result.
"It could be as simple as people who feel in control go out and get the skills they need to manage their asthma, and they work hard on those skills."
Dr Gibson would be speaking about the issue at the New Zealand Respiratory Conference being held in Wellington today and tomorrow.
Seven international and national keynote speakers will make presentations, with many discussing the well-documented link between poor respiratory health and the social determinants of health, and examining new ways to make a difference to health outcomes for sufferers.
Conference presenter Associate Professor Nikki Turner said being sick was not inevitable or just bad luck.
"Living in economic poverty makes people, and children in particular, at much higher risk of being sick," she said.
BY THE NUMBERS IN NEW ZEALAND:
• More than 600,000 New Zealanders have asthma
• 11 per cent of adults and 14 per cent of children take medication for asthma
• It costs $1200 a day to treat a child in hospital with asthma
• There were 8000 asthma hospitalisations and 2800 day cases in 2011
(source: Asthma Foundation)