After adjustment for depression in the other parent and other covariates, we found that indicators of paternal psychosocial stress (PTSD symptoms) and psychiatric disorders (major depressive episode, and anti-social behavior) were significantly associated with recent asthma symptoms in children at age 1 year but not with any asthma outcome in children at age 3 years. Maternal depressive symptoms were significantly associated with asthma hospitalizations at age 1, and both asthma hospitalizations and asthma diagnosis at age 3. Examining the combined outcomes at age 1 and 3 years, paternal depression was associated with recurrent oral steroid use, maternal depressive symptoms with hospitalizations for asthma and asthma diagnosis, and parental depression with hospitalizations for asthma.
To our knowledge, this is the first report of an association between maternal depression and asthma outcomes in childhood after accounting for paternal depressive disorder, as well as the first to report an independent association between indicators of paternal psychosocial stress and asthma outcomes in early childhood. Our findings add to a growing body of literature examining the link between psychosocial stress and asthma morbidity generally, and specifically psychosocial stress in parents and asthma outcomes in their children.
Consistent with prior studies examining maternal (but not paternal) depression,17–19
we found that maternal depression was associated with asthma symptoms, hospitalizations for asthma and asthma diagnosis in childhood after accounting for paternal depression. Previous studies of maternal depression and asthma have assessed children at various age groups and used various indicators of life or psychological stress. Some studies did not control for smoking15, 19
which may partly explain the effects of stress or psychiatric disorders on asthma.35
Together with prior findings, our results emphasize the importance of symptoms of psychosocial stress and not just psychiatric diagnoses in the relationship between stress and asthma.
No prior studies have examined the independent effects of paternal stress on asthma outcomes. Though associations between paternal depression and outcomes at age 3 were not statistically significant, there was a trend towards association with increased use of oral steroids, which may have been significant with a larger sample size. Examining the combined 1 year and 3 year outcomes, paternal depression was strongly associated with recurrent oral steroid use for asthma. Furthermore, no studies have looked at the combined effect of parental depression. We found a significant effect of each additional parent with depression on increased risk of recent asthma symptoms at age 1, and found a trend towards association with steroid use, asthma hospitalizations, and asthma diagnosis at age 3. In the combined analysis, we found a significant effect of parental depression on recurrent hospitalizations for asthma.
Co-morbid asthma and psychosocial stress, and specifically depression, has been well-documented in both children and adults.36, 37
A broad range of biological mechanisms have been implicated in this association.7, 38–42
Parental stress has been associated with altered immune responses relevant to atopic disorders in childhood. Caregiver stress has been associated with elevated total and allergen-specific IgE levels,43
and parental stress has been linked to increased IL-4 and eosinophilic cationic protein release44
in children. Compared to children with acute but no chronic family stress, those with acute and chronic family stress have increased levels of IL-4, IL-5 and IFN-γ.45
Prior studies have shown decreased expression of glucocorticoid and beta-2 adrenergic receptors46
which may lead to decreased response to asthma medications.8
While studies on maternal stress focus on alterations in in utero
exposure to certain hormones as a result of stress, post-natal events such as early life stress resulting from either parent’s behavior can plausibly affect child responses.18
One potentially important mechanism by which this has been shown to occur in animal models is through DNA methylation.47
Behavioral effects may also contribute to the association between parental stress and childhood asthma. Psychological stress, especially depression, may affect parenting skills,48
and affected parents may be less able to supervise their child’s treatment. Alternatively, parental stress may influence the perception or reporting of asthma symptoms in their children.
Our findings have important implications. Discovering modifiable risk factors that can affect immune system development in early life39
is essential in stemming the rising prevalence of asthma and in intervening in particularly vulnerable groups such as Puerto Ricans.5, 49
Island Puerto Ricans may be both more frequently exposed and more susceptible to psychosocial stressors50, 51
than other ethnic groups, with important health consequences in children.52
Psychosocial stress, specifically depression, is treatable and successful therapy of these disorders may impact the lives of parents and children alike.
Strengths of our study include a random sample of children (albeit of twins only) in a group with high asthma prevalence (Puerto Ricans) but no specific bias as to socioeconomic or other factors. In addition, mothers and fathers were questioned independently, rather than having one parent answer for both.
Our study has several limitations. First, the young age of the children precludes an accurate diagnosis of asthma and questionnaires did not differentiate whether wheezing was due to concurrent respiratory infection, a frequent cause of wheezing in young children. However, early childhood wheezing is a risk factor for subsequent development of asthma,53–56
and childhood wheezing and hospitalizations, regardless of whether the children go on to develop asthma, are an important cause of morbidity in young children.57
Having outcomes at both 1 year and 3 years of age, and combining these outcomes, strengthens the analysis as recurrent need for steroids or hospitalizations for asthma makes the diagnosis of asthma more likely. Second, we did not have information on the presence of older siblings, which may affect both parental stress and asthma. Third, some of the measures of psychosocial stress, specifically PTSD and anti-social behavior in fathers and depressive symptoms in mothers, were based on standardized questions but were not part of a diagnostic algorithm. However, our findings suggest that parental symptoms suggestive of these disorders, even without a definitive diagnosis, may be associated with asthma morbidity in childhood. Fourth, associations do not prove causality. Although prior research has shown a bidirectional association between psychosocial factors and asthma,58
we cannot establish whether parental psychosocial stress leads to increased asthma morbidity in young children or vice versa, particularly at age 1 year. Lastly, some data suggests that having twins may increase psychosocial stress for parents.59, 60
If this is the case, our cohort would be enriched cohort to study parental stress and asthma. However, we cannot state this definitively without a control population.
In summary, our study showed a significant association between both maternal and paternal psychosocial stress and asthma morbidity in early childhood. More specifically, both maternal and paternal depression were associated with increased asthma morbidity at 1 year and 3 years of age. Although further studies are warranted, our work suggests that parental psychosocial stress, especially parental depression, may be an important modifiable risk factor for asthma morbidity in childhood, especially in high risk populations.