Children who suffer physical abuse, death of a parent or other childhood adversity and are anxious or depressed are at increased risk of developing asthma in adulthood, a study suggests.

"This is interesting," Dr. Kate M. Scott told Reuters Health, "because, although it has been known for a long time that people with asthma are more likely to also experience some anxiety disorders and possibly depression, it is usually thought that these mental disorders occur as a consequence of asthma."

"It is also well understood that psychological influences like stress or anxiety can exacerbate asthma, but it is rather novel to find suggestive evidence that they may increase the risk of its initial development," added Scott, who is with the Department of Psychological Medicine, at the University of Otago School of Medicine and Health Sciences in Wellington, New Zealand.

"Our research suggests that psychosocial stressors like childhood adversity and mental disorders occurring earlier in life actually increase the risk of the later development of asthma," said Scott.

The findings, published in the journal Psychosomatic Medicine, stem from information gathered from more than 18,000 adults in the Americas, Europe and Asia who were interviewed between 2001 and 2004 as part of the World Mental Health surveys.

According to Scott and colleagues, childhood adversity predicted adult-onset asthma, with increasing risk correlating with a greater number of adversities suffered in childhood. These adversities included physical or sexual abuse, neglect, parental death, parent divorce, other parental loss, parental mental disorder, parental substance use, parental criminal behavior, family violence, and family economic adversity.

Anxiety and depressive disorders in childhood also strongly predicted the development of asthma later in life, Scott and colleagues found. The presence of both childhood adversity and childhood anxiety or depression also increased the risk of a child suffering from asthma as an adult.

The ties between childhood adversity and anxiety and depression held up in analyses that factored in the impact of smoking on the risk of asthma. This suggests that the relationship between mental disorders and subsequent asthma onset is independent of smoking.

It's unclear if childhood adversity and anxiety and depression actually cause adult asthma, although there are some plausible biological mechanisms to support a causal link.

"Chronic stress and mental disorders," Scott explained, "are known to be associated with deleterious changes in stress hormone pathways and in immune responses, leading to inflammation."

Other research has shown that the developing stress and immune systems in children are particularly susceptible to disruption in early life, Scott pointed out. "This, in conjunction with genetic and environmental factors, may be the basis for the association between stress in early life and later development of medical conditions like asthma."