(CNN) -- Having attention-deficit hyperactivity disorder may make teens less likely to finish high school, says a new University of California, Davis study.The study found almost a third of students with ADHD, don't graduate with their peers. That's high compared with the national high school drop out rate of 15 percent, says lead study author Dr. Joshua Breslau.

When looking at the different types of ADHD, the study found all of the types of ADHD are associated with a high dropout rate.ADHD is a neurobehavioral disorder commonly diagnosed in childhood. People with ADHD have trouble focusing, controlling impulsive behaviors and can be overly active.

"High school dropout rate really is a national crisis. We know that a third of kids nationally who start in ninth grade don't graduate in four years," says Breslau.

The study also found students who use alcohol, smoke cigarettes and use other drugs are more at risk to drop out. According to the National Institute of Health, nearly a quarter of high school students in the U.S. smoke cigarettes and another 8 percent use smokeless tobacco. "Psychiatric disorders have an adverse effect on education, " Breslau says. "There are really two main disorders, ADHD and conduct disorder, and there is an interlinking of smoking and drop out that is troubling...it really suggests that socioeconomic differences in health are already becoming established very early in life in adolescents...whether they smoke is probably the biggest indicator of their health in adulthood."

Researchers say parents need to make sure they are working together with their schools so that the pediatrician and the child's teacher are communicating about the child's medical health and performance in school.

"We need to better integrate school health with what's schools do, education," says Breslau.The study is published online in July in the Journal of Psychiatric Research.