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To meta-analyse or not to meta-analyse: abortion, birth and mental health

Published online by Cambridge University Press:  02 January 2018

Tim Kendall
Affiliation:
National Collaborating Centre for Mental Health, Royal College of Psychiatrists, London, and Sheffield Health and Social Care NHS Foundation Trust
Victoria Bird
Affiliation:
Institute of Psychiatry, King's College London
Roch Cantwell
Affiliation:
Southern General Hospital, Glasgow
Clare Taylor
Affiliation:
National Collaborating Centre for Mental Health, Royal College of Psychiatrists, London, UK
Corresponding
E-mail address:
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Summary

Two recent meta-analyses claim that abortion leads to a deterioration in mental health. Previous reviews concluded that the mental health outcomes following an unwanted pregnancy are much the same whether the woman gives birth or terminates the pregnancy, although there is an increased mental health risk with an unwanted pregnancy. Meta-analysis is particularly susceptible to bias in this area. The physical health outcomes for women with an unwanted pregnancy have improved greatly by making abortion legal. To further improve the mental health outcomes associated with an unwanted pregnancy we should focus practice and research on the individual needs of women with an unwanted pregnancy, rather than how the pregnancy is resolved.

Type
Special article
Copyright
Copyright © Royal College of Psychiatrists, 2012 

In most liberal societies, a woman carrying an unwanted pregnancy can choose to have an abortion, subject to the relevant legal framework (e.g. rules on timing and risk to either the woman or child). Alternatively, she may decide to continue with the pregnancy to birth (or she may miscarry). It is important for a woman to understand the possible physical and mental health risks associated with each action, particularly in the UK and Commonwealth countries where the legal grounds for abortion are to mitigate the likelihood of physical or mental harm to the woman should she continue with the pregnancy. It is also important for women in the US, where there have been recent attempts to introduce more restrictive abortion laws with claims that abortion is damaging to women’s mental health.

It is reasonably well accepted that there is a broad range of physical and mental health risks associated with birth. It is less certain whether the mental health risks associated with birth are altered if the pregnancy is unwanted. Similarly, it is established that there are some physical risks directly related to the timing of an abortion and the techniques used, especially for illegal abortion, Reference Sedgh, Henshaw, Singh, Ahman and Shah1 but we are less certain about the mental health outcomes following the termination of an unwanted pregnancy.

This topic has been the subject of much debate and research. In this Journal, a recent meta-analysis (the first of its kind) comparing mental health outcomes following abortion with other pregnancy outcomes Reference Coleman2 generated considerable disquiet, accusations of bias and suggestions of undeclared conflicts of interest. Reference Howard, Rowe, Trevillion, Khalifeh and Munk-Olsen3Reference Goldacre and Lee6 In a letter of response, Fergusson and colleagues also reported the findings of a meta-analysis of mental health outcomes following abortion. Reference Fergusson, Horwood and Boden7 Coleman and Fergusson appear to agree that abortion is associated with an increased risk to a woman’s mental health. However, two previous systematic narrative reviews Reference Major, Appelbaum, Beckman, Dutton, Russo and West8,Reference Charles, Polis, Sridhara and Blum9 examining very similar studies to Coleman and Fergusson, came to the conclusion that abortion (when compared with birth) did not lead to an increased risk of mental health problems. No doubt these differences stem from the very variable types of studies reviewed and their interpretation.

Narrative and systematic reviews of abortion and mental health

The American Psychological Association’s narrative review set out to ascertain whether there is an increased risk of mental health problems following an abortion compared with birth, and the factors that may be related to such an increased risk Reference Major, Appelbaum, Beckman, Dutton, Russo and West8 (updated by Major et al Reference Major, Appelbaum, Beckman, Dutton, Russo and West10 ). Reviewing 56 studies comparing abortion and other pregnancy outcomes, and 23 with no comparator, they concluded that the relative risk of developing mental health problems following a single, first-trimester abortion of an unplanned pregnancy was no greater than the risk following giving birth.

Charles and colleagues’ Reference Charles, Polis, Sridhara and Blum9 systematic review of more than 700 studies, including only 21 for analysis, compared the longer-term mental health outcomes of abortion with those of birth. The authors developed five quality criteria to rank the studies, such as appropriateness of the comparison group and whether they controlled for pre-abortion mental health status. Using these criteria, four studies were judged to be ‘very good’, eight ‘fair’, eight ‘poor’ and one ‘very poor’. They concluded that restricting the analysis to studies of very good quality resulted in little or no difference in mental health outcome following abortion compared with birth, and that, as the quality declined, there was an increased possibility that studies would conclude that abortion was more likely than birth to end in poor mental health outcomes.

Meta-analyses of abortion and mental health

The Coleman Reference Coleman2 meta-analysis cannot be regarded as a formal systematic review because search strategies and exclusion criteria were not published. Nevertheless, the 22 pooled studies had to: assess the impact of abortion against a no-abortion group; have a sample size of at least 100; use odds ratios; and have been published in English-language peer-reviewed journals between 1995 and 2009. Although studies were required to control for third variables, they were not required to control for mental health problems before the abortion. In addition, the no-abortion groups included ‘no abortion’, ‘pregnancy delivered’ or ‘unintended pregnancy delivered’. Coleman concluded that there was ‘a moderate to highly increased risk of mental health problems after abortion over the risks of birth’. The volume of highly critical letters that followed publication is a testament, not just to the review’s methodological flaws, but also to the personal, ethical, religious and political importance of abortion to different groups.

Fergusson and colleagues Reference Fergusson, Horwood and Boden7 meta-analysed eight studies identified in the three reviews discussed above, comparing abortion versus unwanted/unintended pregnancy, and suggest that, following an unwanted/unintended pregnancy, abortion is more likely than birth to be associated with anxiety, self-harm and substance misuse (but not depression). Although the main analysis did not control for mental health before abortion, a secondary analysis of four studies, which did control for mental health, found that an increased risk of general psychiatric problems remained.

Last year, we completed a systematic review, narrative synthesis and limited meta-analysis of the mental health outcomes following abortion and birth of an unwanted pregnancy. 11 We concluded that the majority of studies in the review were subject to multiple limitations, such as heterogeneity of mental health outcomes and their methods of assessment, inadequate control of confounding variables, and comparator populations that rarely included unwanted pregnancies continuing to birth. For these reasons, our meta-analysis only included four studies, all of which controlled for prior mental health problems and used unwanted/unintended pregnancies for analysis. We found that there were small effects associated with abortion, increasing the risks of self-harm and decreasing risks for psychosis. However, these four studies were conducted in different countries: two Reference Steinberg and Russo12,Reference Cougle, Reardon and Coleman13 in the USA, where abortion is available on-demand, one Reference Gilchrist, Hannaford, Frank and Kay14 in the UK and one Reference Fergusson, Horwood and Boden15 in New Zealand. In the UK and New Zealand the legal grounds for abortion are to mitigate any physical or mental harm should the pregnancy be delivered. Finding that women in these studies had a higher rate of mental health problems after abortion risks the criticism that it would be like finding out that people who took hangover remedies had an increased risk of headache. Reference Dwyer and Jackson16

From abortion to unwanted pregnancy: making sense of the data

A recent prospective, population-based cohort study Reference Munk-Olsen, Laursen, Pedersen, Lidegaard and Mortensen17 used three Danish national registers to identify, and follow, females who had no prior history of mental health problems, and who went on either to have a first abortion or to give birth. The authors estimated the rates of psychiatric contact in the 9 months preceding abortion or birth, and in the subsequent 12 months. They showed that females who had an abortion had significantly higher rates of mental health problems in the 9 months before abortion than those in the 9 months before birth; and that for those who had an abortion, their rates of psychiatric contact after the abortion were no greater than before the abortion. In contrast, females who gave birth had significantly higher rates of mental health problems after birth than before. It is a distinct possibility that mental health problems precede unwanted pregnancy and/or unwanted pregnancy may lead to mental health problems.

In our view, all three meta-analyses Reference Coleman2,Reference Major, Appelbaum, Beckman, Dutton, Russo and West10,11 added little to a well-done narrative review, and risked giving the impression that the results were more scientific and reliable. GRADE evaluation of our meta-analysis suggested that the outcomes were of very low quality and therefore at significant risk of not being correct; a critique likely to be true of Fergusson and colleagues’ meta-analysis. We concluded that the American Psychological Association’s Reference Fergusson, Horwood and Boden7 and Charles et al’s Reference Major, Appelbaum, Beckman, Dutton, Russo and West8 reviews were probably accurate: for a woman carrying an unwanted pregnancy, current evidence suggests that her mental health is probably largely unaffected whether she chooses to have an abortion or to continue to birth. In Denmark, where a woman has the right to choose, and in the UK where the right to choose is curtailed by the requirement for professional approval, two high-quality studies, some 16 years apart, appear to support the general conclusion of these and our review: that there is no or little increased risk of mental health problems following abortion. Reference Gilchrist, Hannaford, Frank and Kay14,Reference Munk-Olsen, Laursen, Pedersen, Lidegaard and Mortensen17

Unwanted pregnancy is both a potential personal catastrophe and a major public health problem, leading to over 46 million abortions each year worldwide, of which over 19 million are illegal abortions. 18 In the UK before the Abortion Act 1967 there were an estimated 100 000 illegal abortions each year. 19 The vast majority of unsafe/illegal abortions now occur in low- and middle-income countries, with a mortality rate between 100- and 1000-fold greater than legal abortions; however, the mortality rate for illegal abortions in the USA is still 50 times greater than that for legal abortions. Reference Sedgh, Henshaw, Singh, Ahman and Shah1 Making abortion legal has helped to substantially reduce the physical health risks for women with an unwanted pregnancy; perhaps moving our attention from what all too often appears to be morally and politically influenced concerns about abortion, we could focus on the mental health needs associated with unwanted pregnancy both in clinical practice and research.

Footnotes

Declaration of interest

T.M., V.B., R.C. and C.T. have been funded by the Academy of Medical Royal Colleges (AoMRC) to undertake a review of mental health and abortion. R.C. is Chair of the expert reference group for the AoMRC, and is Chair of the Section of Perinatal Psychiatry of the Royal College of Psychiatrists.

References

1 Sedgh, G, Henshaw, S, Singh, S, Ahman, E, Shah, IH. Induced abortion: estimated rates and trends worldwide. Lancet 2007; 370: 1338–45.CrossRefGoogle ScholarPubMed
2 Coleman, PK. Abortion and mental health: quantitative synthesis and analysis of research published 1995–2009. Br J Psychiatry 2011; 199: 180–6.CrossRefGoogle ScholarPubMed
3 Howard, LM, Rowe, M, Trevillion, K, Khalifeh, H, Munk-Olsen, T. Abortion and mental health: guidelines for proper scientific conduct ignored (letter). Br J Psychiatry 2012; 200: 74.CrossRefGoogle Scholar
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8 Major, B, Appelbaum, M, Beckman, L, Dutton, MA, Russo, NF, West, C. Report on the APA Task Force on Mental Health and Abortion. APA, 2008.Google Scholar
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