School of Population Health
School of Pharmacy
School of Population Health and School of Social Science
School of Population Health, University of Queensland, Brisbane, Australia
Correspondence: Kaeleen Dingle, Level 2, Public Health Building, School of Population Health, University of Queensland, Herston Road, Herston, QLD 4006, Australia. Email: s4002827{at}student.uq.edu.au
None. Funding detailed in Acknowledgements.
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Recent evidence has linked induced abortion with later adverse psychiatric outcomes in young women.
Aims
To examine whether abortion or miscarriage are associated with subsequent psychiatric and substance use disorders.
Method
A sample (n=1223) of women from a cohort born between 1981 and 1984 in Australia were assessed at 21 years for psychiatric and substance use disorders and lifetime pregnancy histories.
Results
Young women reporting a pregnancy loss had nearly three times the odds of experiencing a lifetime illicit drug disorder (excluding cannabis): abortion odds ratio (OR)=3.6 (95% CI 2.0–6.7) and miscarriage OR=2.6 (95% CI 1.2–5.4). Abortion was associated with alcohol use disorder (OR=2.1, 95% CI 1.3–3.5) and 12-month depression (OR=1.9, 95% CI 1.1–3.1).
Conclusions
These findings add to the growing body of evidence suggesting that pregnancy loss per se, whether abortion or miscarriage, increases the risk of a range of substance use disorders and affective disorders in young women.
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Measurement of psychiatric disorders
At 21-year follow-up, the lifetime version of the Composite International
Diagnostic Interview computerised version (CIDI– Auto, version
2.1)12 was used to
assess psychiatric disorders. The CIDI has been found to have good reliability
and validity.13 The
study reports six
DSM–IV10
disorders: total affective and anxiety disorders; alcohol, cannabis and other
illicit drug use and dependence disorders, as well as nicotine withdrawal and
dependence disorders. The age at first onset of disorder and disorders
occurring within the previous 12 months were used. Although we had intended to
explore associations between pregnancy outcomes and specific psychiatric
disorders such as psychosis, only 21 women met DSM–IV criteria for any
psychosis. We were, therefore, unable to undertake meaningful analysis of the
influence of pregnancy outcomes on psychotic disorders.
Measurement of pregnancy outcomes
Women reported the number of previous pregnancies, abortions, miscarriages
and births they had experienced by age 21. We created a variable which
incorporated all four possibilities (never pregnant, live birth only, ever had
an abortion and ever miscarried) (Fig.
1). Seventeen women had both an abortion and miscarriage: for the
analysis, six women who had miscarried two or three times were coded to
miscarriage, five women who had had two abortions were coded to abortion, and
the remaining six women with one abortion and one miscarriage were randomly
assigned to either the abortion or miscarriage group. Those with missing data
in any of the questions were excluded.
![]() View larger version (25K): [in a new window] [as a PowerPoint slide] |
Fig. 1 Pregnancy outcomes for 280 women reporting a pregnancy at 21 years (n=1223,
excludes 943 never pregnant women, includes 17 women who had both an abortion
and miscarriage).
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Confounders
Confounders included maternal and familial factors, measures related to
pre-existing behaviour problems and substance misuse, as well as demographic
characteristics of the young women.
Young womens early life and family background
Symptoms of anxiety and depression experienced by the young womens
mothers during pregnancy were assessed using the two seven-item sub-scales of
the Delusions-Symptoms-States Inventory
(DSSI).14 The
depression sub-scale strongly correlates with DSM–IV major depressive
disorder.15 Mothers
were classified as anxious or depressed if they reported four or more
symptoms. Maternal smoking was assessed pre-pregnancy and at birth. At 14-year
follow-up, mothers indicated if they lived with the young womens
biological father, lived alone or with others. Mother–child
communication was measured with a problem communication sub-scale from the
Parent–Adolescent Communication Scale
(PACS).16 Family
socio-economic status was assessed by yearly family income and maternal
education at baseline.
Adolescent behaviour
At age 14, we used maternal reports of the young womens
delinquent/aggressive behaviour from the Achenbachs Child Behavior
Checklist (CBCL) and the Youth Self-Report (YSR) anxious/depressed
sub-scale.17 The
checklists are widely used, standardised scales that are reliable, valid
indicators of problem
behaviour.18 At 14,
the young women were asked to define their overall school performance (average
or below and above average).
At age 21, participants were asked whether they used cannabis and the age this was initiated. Participants were also asked the age at which they first had sexual intercourse, women reporting no sexual intercourse were excluded. A history of exposure to sexual violence or child sexual abuse and the age this first occurred was obtained with items from the Los Angeles epidemiologic catchment area project.19 Child sexual abuse was defined as unwanted sexual contact before 16 years of age with a person 5 or more years their senior. Young women were also asked if they had ever been raped.
Demographic factors at age 21
Demographic factors included age, marital status, age of leaving the family
home, living arrangements (parents/relatives, renter, boarder or owner) and
education level at age 21.
Statistical analysis
Chi-squared tests and logistic regression were used to explore the
bivariate associations of pregnancy outcomes and each DSM–IV disorder.
We then fitted multivariate logistic models on a restricted sample of young
women (n=1223) with complete data for each DSM–IV disorder
separately. Associations with each disorder were adjusted consecutively for
maternal and family factors at baseline and 14-year follow-up (model 1),
adolescent behaviour problems at 14 (model 2), adolescent behaviour reported
at 21 (model 3) and concurrent demographic factors (model 4). Clearly
non-significant factors (P>0.1 or those with unstable estimates as
assessed by large standard errors) were removed. Each model was reassessed
until only significant effects (P<0.05) remained. This was
undertaken separately for each of the six DSM–IV disorders. Unadjusted
and adjusted odds ratios (OR) and 95% confidence intervals were used to
estimate the association between pregnancy outcomes and each disorder compared
with the never pregnant group. All pairwise pregnancy outcome comparisons were
undertaken with each of the fully adjusted models.
Sensitivity analyses
A series of sensitivity analyses were done to further explore the timing of
the associations and effects of substance misuse, behaviour problems and
psychiatric morbidity that possibly preceded pregnancy loss. Factors such as
adolescent cigarette smoking, alcohol consumption and anxious/depressed and
aggressive/delinquent behaviour were excluded from the model as these are
possible causal factors associated with later psychiatric morbidity. Six
separate sensitivity analyses were conducted:
Finally, we used inverse probability weighting20 to determine whether loss to follow-up affected the validity of our findings. This was done for the six DSM–IV diagnoses both lifetime and current (12-month) disorders. Analyses were carried out using SPSS version 15.0 and STATA version 9.0 on Windows.
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Associations between pregnancy and psychiatric disorders
The unadjusted odds of having a lifetime psychiatric or substance use
disorder were highest among women reporting a pregnancy loss and lowest among
women who never had a pregnancy or gave birth; women with a nicotine disorder
were the exception. Women with a history of abortion or miscarriage were twice
as likely to meet criteria for alcohol, cannabis, other illicit drug use,
depressive or anxiety disorder compared with those who were never pregnant or
who had given birth (Table 1).
Young women who became pregnant regardless of outcome had similarly high odds
of having a lifetime tobacco dependency compared with never pregnant
women.
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View this table: [in a new window] | Table 1 Rates of psychiatric disorders and substance use disorders at 21, by history of birth, abortion or miscarriage (n=1223) |
Adjustment for confounding
Online Table DS2 shows associations between pregnancy outcomes and a number
of potential confounding factors. Pregnancy outcomes were associated with
greater social and economic disadvantage, family instability, alcohol and
cigarette use, aggressive/delinquent behaviours, early sexual intercourse and
poorer educational outcomes at both age 14 and 21. There were only modest
differences between women reporting an abortion and those with a history of
miscarriage or birth.
Table 2 shows the multivariable logistic regression analyses. Women reporting a pregnancy were twice as likely to develop a tobacco dependency, with the association being slightly attenuated by adjustment for maternal and family factors and adolescent behaviour. Women who reported an abortion had twice the odds of having an alcohol disorder and nearly four times the odds of an illicit drug use disorder (excluding cannabis). Also, those reporting an abortion had an increased risk of affective disorder, although this association bordered significance after adjustment for 21-year demographic factors. Women who reported a miscarriage had a similarly high risk of developing an illicit drug use disorder, but not affective or alcohol disorders, as women reporting an abortion.
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View this table: [in a new window] | Table 2 Associations as odds ratio (OR) (95% CI) for lifetime DSM–IV disorders in young women who reported a birth, abortion or miscarriage (n=1223) |
Comparison testing of pregnancy outcomes
For all psychiatric outcomes, except for tobacco dependence, pairwise
comparisons show that risk did not vary significantly between the never
pregnant and live birth groups (P>0.15) and importantly, between
women reporting either a miscarriage or abortion (P>0.40). Young
women reporting a pregnancy regardless of outcome were at least twice as
likely to have a tobacco dependency disorder as never pregnant women
(P<0.02) and the risk of disorder did not vary between pregnancy
outcomes (P>0.64). Women reporting a pregnancy loss were at
increased risk of affective disorders, irrespective of whether the loss was
due to abortion (P=0.02) or miscarriage (P=0.05). Those
reporting having an abortion were also more likely to develop an alcohol
disorder (P=0.02) or an illicit drug use disorder (P=0.02),
although not a cannabis disorder, than women giving birth (online Table
DS3).
Sensitivity analyses
In this birth cohort study, DSM–IV diagnoses and pregnancy outcomes
were concurrently measured, making the direction of the associations difficult
to determine. Therefore a series of six sensitivity analyses were undertaken.
When we excluded women with complex pregnancy outcomes (17 participants
reporting both an abortion and miscarriage and 68 reporting one or more types
of pregnancy loss as well as a birth) there was no substantial change to our
results, with the exception of the association between abortion and anxiety
disorder, which became significant (OR=1.6, 95% CI 1.1–2.7) when
individuals with abortion and miscarriage were removed, although the same was
not seen when women reporting at least one birth and pregnancy loss were
removed. Exclusion of participants reporting cigarette and alcohol use,
anxious/depressed behaviour and aggressive/delinquent behaviour at 14 yielded
similar results to those presented in Table
2.
As timing of the pregnancy was not recorded, young women reporting onset of a disorder at or before the age of their debut sexual intercourse were excluded. The majority of young women had onset of DSM–IV depression (55.8%, n=192) and anxiety (87.6%, n=366) before they started having sexual intercourse. Removal of those with early onset strengthened associations between abortion and depression (OR=1.9, 95% CI 1.1–3.3) and all the pregnancy outcomes and anxiety (OR=2.9, 95% CI 1.2–6.7). The remaining results were essentially unchanged from those reported in Table 2 (online Table DS4).
A sensitivity analysis using current (12-month) DSM–IV disorders was conducted to better account for the temporal sequence of pregnancy outcomes, psychiatric and substance use disorders. The findings were not substantially different from Table 2, except the association between abortion and current affective disorder became significant (OR=1.9, 95% CI 1.1–3.2) (online Table DS5).
Attrition
There was significant loss to follow-up between the 14- and 21-year
surveys. To determine if loss to follow-up at 21 years affected the validity
of our findings, we conducted a sensitivity analysis using inverse probability
weights20 modelling
the probability of having missing data at age 21. Relevant variables available
at baseline were included in an exploratory regression model to determine
whether individuals remaining in the study significantly differed from those
lost to follow-up. Loss to follow-up at age 21 was predicted by being the
child of a teenage mother (OR=1.8, 95% CI 1.5–2.0) who smoked (OR=1.4,
95% CI 1.3–1.7) and reported anxiety symptoms during pregnancy (OR=1.4,
95% CI 1.2–1.7) (online Table DS1). When weights using factors that
predicted missing data at age 21 were included in all adjusted models, the
results were virtually the same as those presented here, except the
association between lifetime alcohol dependency and miscarriage became
significant (OR=1.9, 95% CI 1.1–3.5) (online Table DS5).
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Two prospective longitudinal studies, one from New Zealand2 and the other from Norway,3 used standardised psychiatric interviews to examine a range of psychiatric and substance use disorders following abortion. Both found evidence of a causal association between abortion and later psychiatric and substance use disorders after controlling for a wide range of pre-pregnancy factors including pre-existing mental health. The New Zealand birth cohort study followed 506 women and found those reporting an abortion before age 21 had significantly higher rates of depression, anxiety, alcohol and illicit drug use by age 25 compared with women who had never been pregnant or women who had given birth.2 The Norwegian study followed 769 young women from age 15 to 27 and found abortion before age 20 was associated with later nicotine dependence, alcohol, cannabis and other illicit drug use in women having no stable relationship with the biological father.3 Our study found that women having an abortion had an increased risk of both lifetime and current DSM–IV diagnoses of alcohol, illicit substance use and current affective disorders but women giving birth had no such increased risk, except for tobacco dependency. Contrary to Pedersen,3 we found no association between abortion and cannabis disorder.
Despite this, our findings challenge the existing evidence of a causal link between nicotine,3 other illicit drug use, alcohol use disorders and abortion.2 Pairwise comparisons found that pregnancy outcomes were all equally associated with tobacco dependence; abortion and miscarriage exhibited similar associations with lifetime and current other illicit drug and lifetime alcohol use disorders. To date, no population-based study has compared adverse risk of psychiatric and substance use disorders in women reporting miscarriage and induced abortion. This study is the first large longitudinal cohort that has found a similar pattern of increased risk of alcohol and other illicit drug use disorders in women reporting either abortion or miscarriage compared with women who were never pregnant or had given birth. The findings suggest that the poor outcomes reported for women who had an induced abortion may be associated with pregnancy loss rather than simply the experience of abortion. Induced abortion and miscarriage are both stressful life events that have been shown to lead to anxiety, sadness and grief 5,22 and, for some women, serious depression and substance use disorders.22–24 Although we were not able to fully explain the mechanisms behind these associations, a number of possible pathways were explored in sensitivity analyses. Early heavy alcohol, illicit drug use and depression have been linked to risky sexual activity, unwanted pregnancies and pregnancy complications,24,25 and could be on the causal pathway leading to both pregnancy loss and adverse psychiatric outcomes. After taking these factors into account and removing early onset disorders our findings remained robust. This suggests that our results were unlikely to be explained by reverse causality. Pregnancy loss and substance misuse may have shared risk factors. Unplanned pregnancy commonly co-occurs with individual and social risk factors such as early sexual activity, poor school performance, cigarette smoking, alcohol and illicit drug taking and behaviour problems.21,24,26 Although we may have not been able to control for all confounding, associations in our study remained robust after adjustment for a wide range of such potential confounding factors. Finally, pregnancy loss may be directly associated with an increased risk of later substance misuse, particularly if alcohol and illicit drugs are used to decrease emotional responses to the loss.2,3,27–29 Future longitudinal studies are needed to better understand the relationship of pregnancy loss with adverse psychiatric outcomes in young women.
Limitations
This study has a number of limitations. Contextual information related to
circumstances of the pregnancy loss were not collected, so we could not
account for associated factors such as reasons to abort, support received and
gestational age at the time of the pregnancy loss. We had no access to medical
records to investigate whether specific circumstances surrounding the
termination, the timing of termination or other pregnancy-related events would
confound associations between pregnancy loss and psychiatric disorders.
Concern about possible underreporting of abortion has been
raised.2,30
Data on abortion history was collected from a self-reported survey, and Jones
& Kost31 found
this method provides a more accurate abortion history than face-to-face
interview. Women may have misclassified induced abortions as miscarriages;
however, this appears unlikely as the reported rate of miscarriage was no
higher than
expected.32 It is
also possible that the use of retrospective recall and concurrent assessment
of pregnancy outcomes and DSM–IV disorders introduced some bias in our
findings, although sensitivity analysis using more recent onset psychiatric
disorders produced the same results as those shown in our main analysis. The
high rate of attrition between the 14- and 21-year follow-up raised the
possibility of bias in estimation of the magnitude of risk. Weighted analysis,
which adjusted for factors associated with attrition at age 21, was not
substantially different from the reported findings, which suggests that
attrition bias is unlikely to have produced bias in our results. Finally, ours
is a study of young women whose ages ranged from 18 to 23 years and therefore
our results should not be generalised to older women or women of all ages.
Our study found that young women had similar increased risks of lifetime and current tobacco use, alcohol dependency and illicit substance use, although not cannabis, after an abortion or miscarriage compared with women who had never been pregnant. These associations may relate to common factors associated with pregnancy loss or early pregnancy, rather than being caused by the experience of induced abortion.
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Related articles in BJP:
This article has been cited by other articles:
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S. Rowlands and K. Guthrie Abortion and mental health The British Journal of Psychiatry, July 1, 2009; 195(1): 83 - 83. [Full Text] [PDF] |
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D. M. Fergusson, L. J. Horwood, and J. M. Boden Authors' reply: The British Journal of Psychiatry, July 1, 2009; 195(1): 83 - 84. [Full Text] [PDF] |
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