Being diagnosed with Attention Deficit Disorder can significantly increase the chances of taking up smoking. According to a new study, both ADHD and smoking share a common genetic factor.

Researchers say that people with ADHD are more likely to take up smoking when they are young and smoke twice as much as people without ADHD, HealthDay reported. Once started, people with ADHD also tend to find it difficult to quit smoking.

Attention Deficit Hyperactivity Disorder is a common childhood disorder. Children who have ADHD have difficulty controlling their actions and paying attention. They are easily distracted and cannot focus on a single task.

The genetic variation - rs1329650 - earlier known to be associated with smoking was also related to ADHD. The C* risk allele was the most common factor associated with ADHD along with other learning problems like attention, planning ability, and flexibility.

The study by Ridha Joober and colleagues from the Douglas Mental Health University Institute in Montreal is published in the journalĀ Archives of Disease in Childhood. Although the study shows that there is an association between smoking and ADHD, it doesn't show a cause and effect relation.

The study involved 450 children who were diagnosed with ADHD along with their parents and siblings. Blood samples were taken from all study participants and were analyzed for genetic markers that are associated with different aspects of smoking. Mothers of these children were asked about their own smoking behaviors during pregnancy.

Researchers found that the variation was as likely to be found in children born to women who smoked as in children of women who didn't smoke, suggesting that mother's use of tobacco during pregnancy did not increase the child's risks of becoming a smoker later.