TUESDAY, Oct. 30 (HealthDay News) -- Smoking and
attention-deficit/hyperactivity disorder (ADHD) share a common
genetic risk factor, and childhood ADHD may increase the likelihood
of smoking later in life, a new study suggests.
People with ADHD are more likely to start smoking early and to
smoke twice as much as those without ADHD, the researchers
noted.
For the new study, the investigators took blood samples from
more than 450 children with ADHD, aged 6 to 12, and their siblings
and parents. The samples were tested for five genetic variations
strongly associated with different aspects of smoking, such as the
number of cigarettes smoked every day, and taking up and quitting
smoking. The researchers also asked the mothers about their smoking
habits during pregnancy.
A genetic variant associated with the number of cigarettes
smoked by mothers during pregnancy was more likely than other
variants to be associated with ADHD. It was also more likely to be
passed on from parents to children and to be associated with more
severe ADHD.
This variant was as likely to be found in children whose mothers
smoked as it was in those whose mother's did not smoke during
pregnancy, which suggests that exposure to tobacco smoke in the
womb is not a factor.
The findings suggest that this genetic variant may increase the
risk of both ADHD and smoking by prompting behaviors and impaired
higher brain function that are typical of childhood ADHD, and which
could lead to smoking later in life, concluded Dr. Ridha Joober, of
the Douglas Mental Health University Institute in Montreal, and
colleagues.
The study was published online Oct. 29 in the journal
Archives of Disease in Childhood.
Although these are intriguing findings, further research is
needed to determine whether there are actually shared genetic risks
for smoking and ADHD, Miriam Cooper and Anita Thapar, of Cardiff
University School of Medicine in Wales, wrote in an accompanying
editorial.
Such research could lead to a better understanding about
developmental and psychiatric disorders in children, the
editorialists added in a journal news release.
Although the study found an association between the genetic
variant and ADHD and smoking behaviors, it did not prove a
cause-and-effect relationship.
More information
The U.S. National Institute of Mental Health has more about
ADHD.