Study design: prospective cohort study nested within an RCT.
Participants
Study population
Postpartum women registered with general practitioners in 77 collaborating practices in the UK located in Bristol (21 practices), London (Croydon and Bromley) (21 practices) and Manchester (35 practices) were eligible for the trial. These practices served a wide range of neighbourhoods including both affluent and socioeconomically deprived urban areas. Recruitment took place between January 2005 and Aug 2007,
Inclusion criteria: recently-delivered women aged 18 years or over who had a live birth and were living with their baby.
Exclusion criteria: women who had a stillbirth or neonatal death; women whose baby was more than 26 weeks old or whose baby had been fostered or adopted; women with psychosis, alcohol or drug abuse; women receiving treatment for depression.
Recruitment procedure (see figure 1)
Initial postal screening
All eligible women were identified by clerical assistants at their registered general practice (primary health care centre) as notification of all births is sent to the practices by maternity services and public health services. Practice health visitors checked that women were eligible before the invitation pack to participate in the main RESPOND trial was sent from the GP just before their baby was six weeks old. This invitation pack included a screening EPDS questionnaire. Responses to the EPDS provided at this stage are used to determine an overall prevalence of suicidal ideation in postnatal women. Only eligible, consenting women who had scored 11 or more on the screening EPDS were invited to participate in a home visit to assess further their eligibility for the main RESPOND trial (see Figure 1).
Home visit (baseline)
Once a potentially eligible woman was identified for entry into the main RESPOND trial, a Research Associate would contact the woman and ask if she agreed to a home visit. If a woman consented this was usually conducted at between eight and ten weeks postpartum; however women could receive a home visit up to 26 weeks postpartum. Women completed a baseline EPDS, the revised computerised Clinical Interview Schedule (CIS-R) [17] and a quality of life measure (SF12) (Ware et al, 1996). However, at the start of the trial, women who scored below 13 on the EPDS were not always asked to complete the CIS-R and SF12 so these data are not available for all women who received a home visit. Demographic data were collected by self-report questionnaire.
Follow-up schedule
Follow-ups were scheduled at 4 weeks and 18 weeks after the home visit for randomised women participating in the RESPOND trial. At these time points, postal questionnaires were sent to collect outcome measurements (including the EPDS and SF-12).
Measures
Diagnosis of depression and assessment for suicidal ideation (see Additional File 1: appendix 1 for protocol of SI care)
The Edinburgh Postnatal Depression Scale (EPDS) [9], a 10 item self-report questionnaire, was used to screen for postnatal depression. The case definition for probable depression is a score of ≥13. 'Suicidal ideation' (SI) was defined as an answer of 'Sometimes' or 'Yes, quite often' to question 10 of the EPDS 'The thought of harming myself has occurred to me'. 'No suicidal ideation' was defined by answering 'hardly ever' or 'never' for question 10. The EPDS was completed at the screening stage, the baseline home visit, and at the 4 and 18 week follow-ups.
The self-administered computerised version of the CIS-R was used at baseline to obtain a more accurate measure of the woman's clinical state, to confirm a diagnosis of depression. The CIS-R is a fully structured psychiatric assessment for 14 common symptoms of depression and anxiety in the week before interview. Suicidal ideation is asked about in the following questions:
Have you felt hopeless at all during the PAST SEVEN DAYS, for instance about your future? (Yes/No)
In the PAST SEVEN DAYS, have you felt that life isn't worth living? (no/sometimes/always)
In the PAST WEEK, have you thought of killing yourself? (no/yes - but I wouldn't commit suicide/yes)
In the PAST WEEK, Have you thought about a way in which you might kill yourself? (yes/no)
We coded this as 0 (no suicidal thoughts) or 1-4 (endorsement of one, two, three or four of the questions above)
Mental and physical health status
Mental and physical health status was assessed at baseline and at both follow-ups and measured using the standard SF-12 version 2 questionnaire [18]. This 12-item measure is a widely used and well validated generic measure of functioning. Mental and physical component scores were calculated using standard algorithms, with higher scores indicating better functioning.
Quality of relationship
Quality of relationship was assessed at baseline and at both follow-ups using the Golombok-Rust Inventory of Marital State (GRIMS) [19]. This instrument is a 28-item questionnaire to assess the overall quality of a couple's relationship with higher scores indicating poorer quality of relationship. The measure has been shown to have good reliability (Cronbach's alpha of 0.92 in men and 0.89 in women).
Socio-demographic measures
Data were also collected on marital and co-habiting status, educational level, employment status of women and partner, ethnicity and parity.
Statistical methods
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).
Ethical approval
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).