Friday June 5 2015
Around 1 in 8 women experience depression during pregnancy
“The seeds of depression can be sown in the womb,” is the claim in the Mail Online.
While a new study did find that depression during pregnancy was linked to an increased risk of depression in adult offspring, a range of factors could be contributing.
The study analysed data collected from 103 pregnant mothers whose mental health was assessed though interviews during pregnancy and up to the time the time their child was 16. The children also answered questions of a similar nature about their mental health once they reached the age of 25. The researchers also assessed whether they had experienced maltreatment.
The odds of children whose mothers were depressed during pregnancy developing depression themselves in adulthood were about three times that of children whose mothers were not depressed during pregnancy. They also had about twice the odds of experiencing maltreatment as a child (not necessarily by the mother).
Analyses suggested that the increased maltreatment might explain the link seen between maternal depression in pregnancy and depression in offspring as adults.
The researchers also make various suggestions as to why the links seen might exist. This included the possibility that maternal depression could impact on the child’s development by increasing levels of stress hormones in the womb; speculation that the Mail seems to have taken as proven fact.
In conclusion, it is not possible to say with certainty that maternal depression during pregnancy was directly causing the increase in depression risk seen.
Irrespective of this, it is important that women who experience depression during pregnancy get appropriate treatment and support.
Where did the story come from?
The study was carried out by researchers from King’s College London and was funded by the Psychiatry Research Trust; the National Institute for Health Research (NIHR)/Wellcome Trust King’s Clinical Research Facility; the NIHR Biomedical Research Centre at South London and Maudsley National Health Service Foundation Trust; the Institute of Psychiatry, Psychology & Neuroscience, King’s College London; and the Medical Research Council United Kingdom.
The study was published in the peer-reviewed medical journal The British Journal of Psychiatry. It has been made available on an open-access basis, so it is free to read online or download as a PDF.
The Mail's reporting of the study is likely to add unnecessarily to expectant mothers’ concerns, as it does not highlight the limitations to the research, and the fact the research doesn't show cause and effect, or whether other factors are playing a role.
Also, the suggestion that “Screening pregnant women for [sic] condition [depression] could stop it being passed on” have not been tested in this study.
What kind of research was this?
This was a prospective cohort study called the South London Child Development Study (SLCDS), which started 1986. It aimed to assess whether a child’s exposure to a mother’s depression during and after pregnancy was linked to their risk of depression in adulthood, and also their risk of maltreatment as a child.
Previous research has shown a link between postnatal depression in the mother and later depression in the child, but no prospective studies have attempted to assess the link between a mother’s depression while pregnant and depression of the child when they reach adulthood.
A prospective cohort study is the best way of conducting such a study, but it still has limitations. Most important of these is the possibility that factors other than the one of interest (maternal depression) are contributing to links seen. When such studies follow up people over a long time period, as this study did, they are also prone to participants being lost to follow-up, which can bias results.
What did the research involve?
The researchers recruited expectant mothers in 1986 at 20 weeks into their pregnancy. They assessed their mental health during and after the pregnancy, up until the child was 16 years old. They also assessed whether the child was maltreated, and the child’s mental health when they reached 25. The researchers then analysed whether maternal depression at any stage was associated with the child’s depression or maltreatment.
Standardised one-to-one interviews were carried out with expectant mothers alone at 20 and 36 weeks, and together with their children at 4, 11, 16 and 25 years. The following were being assessed in these interviews:
- maternal depression during pregnancy (at 20 and 36 weeks)
- maternal postnatal depression (3, 12 and 48 months after birth)
- maternal depression during offspring’s childhood (4, 11 and 16 years)
- offspring maltreatment (up to age 17)
- offspring depression in adulthood (18 to 25 years of age)
The researchers also collected information on other factors that may have contributed to or altered findings (potential confounders) so they could take these into account in their analyses.
Of the 153 women who completed the first interview, 103 (67%) completed the study and had their data analysed.
What were the basic results?
Of the mothers in the sample, 34% experienced depression during pregnancy and 35% suffered postnatal depression. Maltreatment was reported in 35% of offspring and about 38% met the criteria for depression in adulthood.
Before taking into account any potential confounders, children exposed to maternal depression in pregnancy had 3.4 times the odds of developing depression as adults compared to children who had not been exposed (odds ratio (OR) 3.4, 95% confidence interval (CI) 1.5 to 8.1). When taking into account child maltreatment and exposure to maternal depression when aged 1 to 16 years old, this association did not remain.
Children exposed to maternal depression in pregnancy were more likely to experience maltreatment as a child (OR 2.4, 95% CI 1.0 to 5.7). Analyses suggested that the maltreatment might be the “link” between maternal depression in pregnancy and offspring depression in adulthood.
How did the researchers interpret the results?
The researchers conclude that the study “shows that exposure to maternal depression during pregnancy increases offspring vulnerability for developing depression in adulthood”. The authors also state: “By intervening during pregnancy, rates of both child maltreatment and depressive disorders in the young adults could potentially be reduced. All expectant women could be screened for depression and those identified offered prioritised access to psychological therapies – as is currently recommended by the UK guidelines on perinatal mental health.”
This prospective cohort study found a link between depression in the mother during pregnancy and child maltreatment and depression in adulthood. The results suggested that the child maltreatment might be the intermediate “step” or “link” between maternal and offspring depression.
The study has strengths and limitations. The strengths are that it prospectively followed women and their children up over a long time period. The prospective nature of the study is the best way to collect such information. This allowed the study to used standardised diagnostic interviews to collect consistent information from participants.
The main limitation to the study is that we cannot be certain that the links seen are due to a direct effect of maternal depression during pregnancy. While the researchers did explore and take into account some potential confounders, other factors could be contributing. It is likely that a range of environmental and potentially genetic factors may be playing a role, especially for a condition as complex as depression, so it is difficult to disentangle their effects.
Another limitation is the study’s small sample size, and the fact that about a third of participants did not complete it. Also, the rates of depression in the study were relatively high, which the authors suggest might reflect the urban population studied. This means that the results may not be representative of the whole population and therefore may not be generalisable to other groups.
As data was collected by interview, and in some cases was regarding a past period of time, it is possible that participants would not have been truthful or may not accurately recall the information that could affect the results.
It seems that this study has found some association, but we should be cautious about what we conclude. However, it does highlight that many women do experience depression in pregnancy, and ensuring that this is treated appropriately is important to the mother’s health and wellbeing, as well as her child and family.
As the authors mention in their article, the use of antidepressants in expectant mothers is an area of debate, due to the potential for effects on the developing baby. Doctors may decide to prescribe them in situations where the benefits are considered to outweigh the potential risks.
It is also important to note that there are other forms of treatment available, such as talking therapies, including cognitive behavioural therapy. Pregnant women who are concerned that they may be depressed should not be afraid to talk to their healthcare professional about this, to ensure they get appropriate care.