Undergoing induced abortion was not associated with the later development of psychiatric problems, according to a report in the Jan. 27 issue of the New England Journal of Medicine.
In a population-based cohort study of more than 365,000 Danish women who became pregnant between 1995 and 2007, the rate of first-time contact with a psychiatric caregiver was no different in the year following a first-trimester induced abortion than it was during the year preceding the abortion, said Trine Munk-Olsen, Ph.D., of the National Center for Register-Based Research at Aarhus University, Denmark, and her associates.
The investigators undertook this study because previous studies of the issue "have had methodologic limitations, including small and self-selected study samples, low response rates and high dropout rates during the follow-up period, lack of control for potential confounders, and inadequate measures of exposure and outcome variables," they noted.
Their study avoided these limitations by relying on national registry data. Induced abortions are legal in Denmark and are tracked in the national health care registry, as are inpatient and outpatient contacts at psychiatric facilities.
The study included 365,550 Danish women who had no history of mental disorders and who had either a first childbirth or a first-ever first-trimester induced abortion between 1995 and 2007.
Among the 84,620 of these subjects who had a first-trimester induced abortion, the rate of a first inpatient or outpatient psychiatric contact was 1.5% during the following year, which was not significantly different from the 1.0% rate during the 9 months preceding the procedure.
The incidences of psychiatric contacts were 14.6/1,000 person-years before the induced abortion and 15.2/1,000 person-years afterward, a nonsignificant difference, Dr. Munk-Olsen and her associates wrote (N. Engl. J. Med. 2011;364:332-9).
"We performed additional analyses to assess whether the results differed on the basis of the subgroup of mental disorders," but they did not, the researchers said. The findings refute the contention that "there is an overall increased risk of mental disorders after first-trimester induced abortion."
Of interest was another finding that, during the same interval, when 280,930 women gave birth to their first live-born child, the rate of first-time psychiatric contact rose significantly from 0.3% in the year before delivery to 0.7% in the year following delivery. The incidences of psychiatric contacts were 3.9/1,000 person-years before childbirth and a significantly higher 6.7/1,000 person-years after childbirth. Thus, childbirth is related to a significant increase in psychiatric consultations, while induced abortion is not.
Although the rate of psychiatric contact was higher among women who had induced abortions than among those who gave birth, those rates were similarly discrepant before the pregnancies occurred. "This suggests that any propensity toward mental health disorders in women who have induced abortions predates the abortion and indeed may make termination of the pregnancy more likely," Dr. Munk-Olsen and her colleagues said.
"This finding underscores the potential bias of direct comparisons of rates of mental health problems between women who have undergone abortion and those who have given birth," they noted.
One such study found a 30% relative increase in the rate of mental disorders among women having abortions, compared with women not having abortions. "However, the study was performed in New Zealand, where the majority of abortions are authorized on the basis of mental health indications. This restriction in the availability of abortions can introduce bias, since mental health problems observed after an abortion may reflect conditions and characteristics predating the abortion rather than resulting from the abortion," the investigators wrote.
This study was supported by grants from the Susan Thompson Buffett Foundation and the Danish Medical Research Council. One of Dr. Munk-Olsen’s associates reported ties to Bayer Schering Pharma.