Dr. Simone Vigod, a psychiatrist at Women's College Hospital and an adjunct scientist at the Institute for Clinical Evaluative Sciences, and colleagues examined live birth rates from 1999 to 2009 in 4.5 million girls, ages 15 to 19 in Ontario, with and without a major mental health illness.
The study, published in the journal Pediatrics, found young girls with a major mental health illness -- including depression, bipolar disorder and other psychotic disorders -- were three times more likely to become teenage parents.
"Research tells us that young girls are at high risk of pregnancy complications, including preterm birth, poor fetal growth and postpartum depression," Vigod said in a statement. "Add to this a pre-existing mental illness, and these young women are forced to manage significant additional challenges."
Although birth rates in both groups decreased during the 10-year study period, but the gap between the two appeared to be increasing slightly. Among girls with a major mental illness, live births decreased by 14 percent during the study period compared with a 22 percent drop among unaffected girls, Vigod said.
"Although we do know some of the risk factors behind why girls with mental health illness may be at increased risk of becoming pregnant, pregnancy prevention programs in most developed countries have not traditionally considered mental health issues," Vigod said.