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to increase risk for ADHD, or may even represent an alternative etiological pathway
that is sufficient to cause the later development of ADHD in a subset of cases
(Swanson, Oosterlaan, et al., 2000). Children with ADHD or significant attention
problems are also significantly more likely than comparison children to have been
exposed prenatally to alcohol (Mick, Biederman, Faraone, Sayer, &Kleinman, 2002)
or tobacco (Milberger, 1996, 1997). These studies demonstrated that cigarette smoking
and alcohol use during pregnancy significantly predicted the later development of
ADHD even when parental ADHD was controlled, indicating that this relation is not
confounded with the familiality of ADHD.
4.3 Prevalence
A meta-analysis of 175 research studies worldwide on ADHD prevalence in
children aged 18 and under found an overall pooled estimate of 7.2% (Thomas et al.
2015). The US Census Bureau estimates 1,800,000,000 people were aged 5-19
worldwide in 2013. Thus, 7.2% of this total population is 129 million of children
worldwide who have ADHD. Based on DSM-IV screening of 11,422 adults for
ADHD in 10 countries in the Americas, Europe and the Middle East, the estimates of
worldwide adult ADHD prevalence averaged 3.4% (Fayyad et al. 2007).
There is another statistic stated by the National Survey of Children’s Health
(NSCH) 2003-2011. The survey based on parent interviews by highlighting the
following data for children who aged 4-17 (US CDC 2014):
(1) 5.1 million children (8.8% or 1 in 11 of this age group 4-17 years) have a current
diagnosis of ADHD which are 6.8% of children ages 4-10 (1 in 15), 11.4% of children
ages 11-14 (1 in 9), and 10.2% of children ages 15-17 (1 in 10).
(2) The average age of current ADHD diagnosis was 6.2 years, which are “Mild”
ADHD diagnosed at 7 years, “Moderate” ADHD diagnosed at 6.1 years and “Severe”
ADHD diagnosed at 4.4 years.
(3) 3.5 million children or 69% of children with current ADHD were taking
medication for ADHD. Boys (12.1%) continue to be more than twice likely than girls
(5.5%) to have current ADHD. According to parent reports, 6.4 million children (11%
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