INTRODUCTION
Allergy is a hypersensitivity reaction initiated by immunologic
mechanisms.1 The prevalence of allergic diseases is
increasing worldwide, including in Japan. The 1999 International Study
of Asthma and Allergies in Childhood (ISAAC) reported that the
prevalence of atopic dermatitis ranged from <2% in Iran to
>16% in Japan and Sweden among children aged 6-7
years.2 Phase III of the same study completed 7 years
later reported an increase in the prevalence of asthma,
rhinoconjunctivitis, and eczema in many countries; a decrease in
prevalence was reported only for asthma among adolescents aged 13-14
years.3
Previous studies have reported a relationship between childhood
attention-deficit hyperactivity disorder (ADHD) as well as other mental
health problems and allergy. Studies have shown that children with
eczema or atopic dermatitis achieved higher scores on the Strengths and
Difficulties Questionnaire (SDQ), indicating that the presence of eczema
may be associated with worse mental health.4-7 Similar
findings have been reported for conditions such as ADHD and autism
spectrum disorders (ASD) among children with eczema. Children with
atopic dermatitis have been shown to be at increased risk of ADHD or
ASD. 8-13
Similar associations have been reported for asthma and
rhinitis5. A systematic review has found that children
with ADHD had a higher rate of asthma than those without
ADHD.14 A separate meta-analysis suggested that
patients with asthma, particularly those with severe symptoms, should be
considered at higher risk of behavioral difficulties that may
necessitate psychosocial interventions.15 In a
nationwide population-based prospective study, Chen suggested that
asthma was a risk factor for further development of ADHD. In addition,
asthma in very early life has been shown to increase the risk of
developing ADHD during school years.16 Suwan reported
increased rates of allergic sensitization in ADHD
cases.17 The prevalence of allergic rhinitis among
children with ADHD has also been reported as higher than that among
children without ADHD.17 A study based on the Taiwan
National Health Insurance Research Database reported that allergic
disorders, in particular, bronchial asthma and allergic rhinitis, but
not atopic dermatitis, were risk factors for ADHD18.
This evidence notwithstanding, previous studies on the relationship
between allergic symptoms and childhood behavioral problems often failed
to consider the impact of parental factors associated with children’s
psychosocial development. A study by Tokunaga et al. examined the impact
of parenting stress in this context and found that paternal stress was
significantly associated with the risk of child
hyperactivity/inattention, while maternal stress was significantly
associated with difficulties in peer relationships and emotional
symptoms.19 However, it is plausible that parenting
stress is the effect, not the cause, of childhood behavioral problems,
resulting in poorer SDQ scores.. It is also plausible that this
relationship is bi-directional.
This study aimed to investigate the relationship between allergic
symptoms and children’s behavioral problems, adjusting for potential
confounding factors such as demographic characteristics, parenting
stress, and allergy-related variables.