We found that 4% of 4150 women in the community at around 6 weeks postpartum had suicidal ideation (SI) occurring sometimes or quite often, and 9% reported any suicidal ideation. This is a higher prevalence of significant SI than reported by previous studies in Finland and England  and this may reflect our study sample which was recruited from areas with higher levels of socioeconomic deprivation than in previous studies . Endorsement of 'yes, quite often' SI on question 10 of the EPDS was associated with affirming at least two CIS-R items on suicidality. However, endorsement of 'sometimes' experiencing SI was not concordant with suicidality as measured by the CIS-R; the kappa statistic of 0.42 reflects this moderate level of agreement. We also confirmed that in women with an EPDS > 12 and a diagnosis of depression, women participating in a treatment trial for postnatal depression were more likely to experience SI if they had more depressive symptoms as measured on the EPDS; in addition they were more likely to be younger, unmarried, unemployed or have an unemployed partner, and have marital problems. In the multivariable analysis, younger age, having 3 or more children and a higher EPDS remained significantly associated with SI. However, SI at baseline was not associated with poorer outcome on follow-up, and this probably reflects the fact that these were women treated for depression in the RESPOND trial (either by medication or psychotherapy).
Strengths and Limitations
This study is one of the largest studies of suicidal ideation in women in the postpartum period in the literature and the only study to compare the EPDS measure of suicidality with another measure of suicidality (the CIS-R). The main limitation of this study is that, like all previous studies, the EPDS suicidality measure is of self reported thoughts of self harm. Self report may lead to under-reporting of actual suicidal thoughts, though it is also possible that self report may more accurately reflect the truth than clinical interviews. There is some evidence that the rate of SI endorsement on self-administered scales can be considerably higher than on clinician-administered scales in perinatal women . We did not measure suicide attempts (which may be of more clinical importance), and previous research has found that 16.7-27.8% of pregnant women referred to a tertiary clinic for neuropsychiatric evaluation endorsed SI, but only one attempted suicide . Nevertheless, there is evidence that suicide ideators and attempters are a separate but overlapping population from those who die by suicide . There is therefore value in investigating suicidal ideas, particularly as much larger samples would be needed to investigate suicide attempters in an epidemiologically representative population. One final caveat though is that the EPDS question on suicidality (item 10) does not explicitly refer to suicide; rather it asks about harming oneself. As has been pointed out in a review of suicidality in the perinatal period , self-harming impulses may or may not reflect intent to die; other dimensions of suicidality, such as reasons for dying and reasons for living, are also needed for more precise risk assessment. The discrepancy found here between women reporting "hardly ever" having thoughts of harming themselves on the EPDS but on the CIS-R reporting that they had thought of killing themselves in the last week, suggests that women are not equating the two statements, and item 10 of the EPDS therefore may not be the best measure of suicidality.
Other limitations include possible selection bias - our estimate of prevalence of SI in the screened population was carried out in women not receiving treatment for depression and this selection bias needs to be borne in mind when interpreting our results. In addition, as with most other studies in this area, the analyses of correlates of SI were limited by the small numbers reporting SI. Finally there are limits on the external validity of this study as our findings on persistence and correlates of SI were carried out on the women who entered the RESPOND trial and may not be generalisable to women outside of a treatment trial.
The clinical significance of SI as measured by the EPDS is not entirely clear, as discussed above. Nevertheless, endorsement of the 'often' experiencing SI item on EPDS was associated with at least two of the CIS-R items of suicidality. Although it remains unclear whether the EPDS should be used routinely in perinatal practice , maternity and community services internationally use this instrument to screen for perinatal depression. The endorsement of question 10 on suicidal ideation can cause major concern for healthcare professionals in these settings who do not usually have mental health training and do not know how to address this in their clinical practice. They may also be concerned about the impact on patients of being asked such a question and fear that asking a question about suicidal thoughts could 'induce' suicidal thoughts and behaviour; however a recent RCT of screening for suicidal ideation in primary care found no evidence to support the view that such screening leads to an increase in feelings that life is not worth living .
This study suggests that these professionals should be aware that endorsement of "often" will usually mean there is significant suicidality and depressive symptomatology warranting referral to an appropriate professional (e.g. general practitioner) for further assessment. However, suicidal ideation does not appear to predict poor outcomes in women who are treated for depression. Women with depressive symptoms and suicidal ideation should benefit from appropriate treatment for postnatal depression such as health visitor delivered non-directive counselling, cognitive behavioural therapy or antidepressants . Women may have strong preferences regarding these treatments and where possible their preferred treatment should be offered as this may improve outcome further [[16, 23, 24]].