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Is season of birth a risk factor for attention-deficit hyperactivity disorder?
E Mick1, J Biederman, S V Faraone
1Pediatric Psychopharmacology Unit, Massachusetts General Hospital, Boston 02114, USA.
Insights
Birth season may influence subtypes of attention-deficit hyperactivity disorder (ADHD). Specific birth months showed increased ADHD risk, particularly for children with learning disabilities or without psychiatric comorbidity.
Area of Science:
- Neurodevelopmental disorders
- Pediatric psychiatry
- Epidemiology
Background:
- Attention-deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder.
- Understanding ADHD etiology involves exploring various risk factors, including potential environmental influences.
- Seasonal birth patterns have been investigated in relation to several neurodevelopmental and psychiatric conditions.
Purpose of the Study:
- To examine seasonal birth variations in children diagnosed with ADHD compared to a control group.
- To investigate the influence of comorbidity, familiality, and learning disability on potential seasonal birth effects in ADHD.
- To identify specific birth seasons associated with increased risk for ADHD subtypes.
Main Methods:
- A cohort of boys diagnosed with DSM-III-R ADHD (n=140) and normal controls (n=120) were studied.
- ADHD subjects were stratified based on psychiatric comorbidity, learning disability, and family history of ADHD.
- Logistic regression analysis was employed to calculate relative risks associated with birth season.
Main Results:
- No overall significant seasonal birth effect was found for ADHD versus control children.
- September births were significantly associated with ADHD in children with learning disability (OR=5.4) and without psychiatric comorbidity (OR=4.5).
- A trend suggested increased risk for ADHD with learning disabilities, no comorbidity, and positive family history during winter births.
Conclusions:
- Preliminary findings indicate a potential seasonal birth pattern for specific ADHD subtypes.
- Season of birth may serve as an indirect marker for seasonally influenced factors, such as viral infections, in ADHD etiology.
- Further research is warranted to elucidate the role of seasonal influences in the pathophysiology of ADHD.
Objective:
To investigate seasonal variations in the birth patterns of children with attention-deficit hyperactivity disorder (ADHD) in reference to a group of normal control children, attending to issues of comorbidity, familiality, and learning disability.
Method:
Subjects were boys with DSM-III-R ADHD (n = 140) and normal controls (n = 120). The ADHD children were stratified by the presence of comorbid psychiatric disorders, learning disability, and family history of ADHD, and logistic regression was used to estimate relative risks.
Results:
No statistically major effect for season of birth was observed in the comparison of ADHD and control children. However, significant effects were found for September births for ADHD children with learning disability (odds ratio = 5.4) and for ADHD children without psychiatric comorbidity (odds ratio = 4.5). A trend was also noted for winter births in ADHD children with learning disabilities, no psychiatric comorbidity, and positive family history for ADHD.
Conclusions:
These preliminary results suggest that there may be a seasonal pattern of birth for subtypes of ADHD. If season of birth serves as a proxy for the timing of seasonally mediated viral infections, it may lead to a greater understanding of the etiology and pathophysiology of ADHD.