The prevalence of suicidal ideation identified by the Edinburgh Postnatal Depression Scale in postpartum women in primary care: findings from the RESPOND trial

We defined suicidal ideation (SI) in these women as the thought of harming themselves "sometimes" or "quite often" as indicated in the response to question 10 of the EPDS. We defined a 'suicidal case' as measured by the CIS-R as identifying 2 or more items on the CIS-R. The outcome measures investigated in the sub-group of women who participated in the RESPOND trial were the SF-12 physical health subscale, SF-12 mental health subscale and EPDS at 18 weeks.

We estimated the prevalence of SI in the complete sample of all women surveyed at the point of screening, using frequencies and proportions. We investigated the persistence of SI in the sub-group of women who entered the trial and were followed up to 18 weeks, by the association between SI in women at home visit baseline, with SI 4 weeks and 18 weeks later using chi-squared tests for the two outcomes, with and without adjustment for treatment allocation. To assess the agreement between the CIS-R measure of suicidality and EPDS SI in women who had measures of both the CIS-R and the EPDS, we tabulated the two measures on their full scores. We used a chi-square test of the two measures using their full range of categories (0-3 for EPDS and 0-4 for CIS-R) and assessed agreement between suicidal caseness as measured by the CIS-R and EPDS SI using a kappa statistic.

To investigate the ability of SI at baseline to predict outcome at 18 weeks in women who had entered RESPOND study, we first summarised the characteristics (age, ethnicity, marital status, living status, parity, employment, education and health measures) of those with and without SI at baseline, testing for differences using t-tests and chi-squared tests. We employed these measures in a multivariable logistic regression to investigate variables associated with SI in a cross-sectional analysis to be adjusted for as potential confounders in the follow-up analysis. We then investigated baseline predictors of loss to follow up and any factors found to be associated were included in the 18 week analysis. We conducted a linear regression of the clinical outcome measures SF-12 physical health subscale, SF-12 mental health subscale and EPDS at 18 weeks after baseline separately adjusting for the relevant baseline measure, suicidal ideation and treatment allocation and then additionally adjusting for variables associated with baseline suicidal ideation. (No factors were found to be associated with loss to follow-up and so no further adjustment was necessary).

The trial was approved by the Scotland Multi-centre Research Ethics Committee (MREC; reference number MREC/03/0/127) and site-specific approval was obtained from the 10 relevant local ethics committees and 10 Primary Care Trusts (PCTs).

4173 women returned the screening questionnaire and of these, a total of 4,150 women completed the EPDS question relating to suicidal ideation (SI) (n = 23, 0.5% missing) (see Figure 2 for flow chart of women through the RESPOND study). Nine percent (95%CI 8.3% -10.1%) (n = 374) reported any suicidal ideation (including hardly ever) and 4% (95% CI 3.2% - 4.4%) reported that the thought of harming themselves had occurred to them sometimes or quite often. The latter group (i.e. reporting that the thought of harming themselves occurred sometimes or often) are defined in this study as experiencing SI. Of those that had SI at home visit and entered the trial (i.e. had a CIS-R primary diagnosis of depression) (n = 32), 56% also reported it at 4 weeks compared to only 9% of those that did not have SI at baseline (p < 0.001 (either unadjusted or adjusted for treatment allocation). At 18 weeks follow-up, only 15% of those with SI at baseline also had it at 18 weeks, which is not significantly different to those without SI at baseline (6%, p = 0.075 adjusted for treatment allocation, (see table 1). No difference in prevalence of SI reporting was seen between the treatment groups at either baseline (p = 0.635), 4 weeks (p = 0.431) or 18 weeks (p = 0.769) follow-up.

We compared the 5 level CIS-R suicidal ideation measure to the 4 level EPDS suicidal ideation measure (table 2) for those women who had a home visit and were administered both measures (n = 331). We also considered dichotomised definitions of "SI cases" as "sometimes/often have suicidal thoughts" on the EPDS and "CIS-R suicidal casesness as endorsement of 2 or more items on the CIS-R. The two measures are significantly associated (chi² statistic = 145.81, p < 0.001). Almost all (99%) women reporting 'never/hardly ever have suicidal thoughts' on the EPDS question reported positively to 2 or fewer items out of 4 on the CIS-R SI questions. All women who reported significant SI on the EPDS (i.e. often had thoughts of self-harm) reported a score of 2 or more on the CIS-R measure of suicidality. However only 68% of those who "sometimes" considered harming themselves on the EPDS scored positively to 2 or more items on the CIS-R. Defining a suicidal 'case' from the CIS-R as responding positively to 2 or more items agrees with the EPDS definition in 79% of cases and gives a moderate kappa statistic of 0.42.

Women who entered the randomised trial (n = 254) (and therefore had an EPDS≥13 and a CIS-R primary diagnosis of depression at home visit) had more detailed sociodemographic and clinical data, enabling us to examine which sociodemographic and clinical variables were associated with SI in this group at baseline. One woman did not complete question 10 of the EPDS and so was not included, leaving 253 women for the remaining analyses (though not all 253 women completed the baseline SF12 - n = 227; ie 90%). There was a small amount of drop-out over the follow-up period, 218 (86%) participants completed the 4 week assessment and 206 (81%) completed the 18 week assessment. Comparisons between those with and without follow-up at 18 weeks indicated no baseline variables were significantly associated with attrition at the 5% level of significance.

In the univariate analysis, we found that women were more likely to experience suicidal ideation at baseline if they were younger, unmarried, unemployed or had a partner that was unemployed. They were also more likely to have a higher score on the GRIMS (reflecting poorer quality of the relationship with partner)and the EPDS and lower (worse) score on the SF-12 mental component (table 3). After multivariate analysis, including all measures (age, ethnicity, marital status, living status, parity, employment, educational level and health measures), adjusted odds ratios remained significant for age and EPDS (see table 3)

We found no association between suicidal ideation at baseline and any of the three outcomes at 18 weeks - SF-12 physical or mental health or the EPDS total score, when adjusted only for the baseline measure and treatment allocation (Table 4). After additional adjustment for variables associated with suicidal ideation at baseline and loss to follow-up (age, current employment, partner employment and marital status) there was still no association found between suicidal ideation and outcome.

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 [20]. 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 [20]. Nevertheless, there is evidence that suicide ideators and attempters are a separate but overlapping population from those who die by suicide [21]. 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 [5], 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 [14], 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 [22].

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 [16]. 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].