WEDNESDAY, Sept. 28, 2016 (HealthDay News) -- Women who use hormonal methods for birth control, such as "the pill," may have a slightly higher risk of developing depression -- and teenagers may be most vulnerable, a large study suggests.

Researchers said the findings confirm the link between hormonal birth control and depression symptoms. However, the association does not prove a cause-and-effect relationship.

Manufacturers already list "mood changes," including new or worsening depression, on their products' list of potential side effects.

But this new study of more than 1 million women strengthens the evidence of a connection, said Dr. Ojvind Lidegaard, of the University of Copenhagen, in Denmark.

Lidegaard said women with a history of depression symptoms might want to consider nonhormonal contraception -- such as intrauterine devices (IUDs) that release copper to prevent sperm from fertilizing the egg.

Dr. Jill Rabin, an obstetrician-gynecologist who was not involved in the study, said what's important is having a doctor "you trust" and who will discuss the pros and cons of all birth control options with you.

"We all need to be cognizant of the fact that hormones can have effects on mood," said Rabin, who is co-chief of the division of ambulatory care at Women's Health Programs-PCAP Services, at Northwell Health, in New Hyde Park, N.Y.

Doctors should routinely ask girls and women if they have a history of depression symptoms when discussing birth control options, Rabin suggested.

There are "many choices" when it comes to contraception, she said, including lower-dose hormonal options.

For the study, Lidegaard's team used Denmark's system of national health databases to track more than 1 million women aged 15 to 34 between 2000 and 2013. They were followed for six years on average.

During that time, women on hormonal birth control were anywhere from 23 percent to two times more likely to start an antidepressant, compared with women not on hormonal contraceptives.

And the risks were larger when the researchers focused on teens aged 15 to 19.

Teenagers using hormonal patches or vaginal rings, or IUDs containing progestin, were roughly three times more likely to be prescribed an antidepressant, versus other teens, the findings showed.