Table 1 Standardised instruments and their psychometric properties

Primary outcome

Common mental disorders

Composite International Diagnostic Interview (CIDI) [58]

Widely used, completely structured lay-administered clinical interview that yields DSM-IV and ICD-10 diagnoses through algorithms.

Concordance between CIDI diagnoses and Structured Clinical Interview for DSM-IV (SCID)

diagnoses of depression (κ = 0.54) and anxiety disorders (κ = 0.48) [70].

Baseline factors

Personality factors which might increase vulnerability to mental health problems

Vulnerable Personality Style Questionnaire (VPSQ)

Vulnerability Subscale measures over-sensitivity to the opinions of others and lack of assertiveness

Range of scores 6 to 30

Cronbach's α for internal consistency 0.77; test - retest reliability 0.82 p < 0.01, in a model predicting postnatal depression sensitivity 0.14 and specificity 0.94 [71]; correlation with self-esteem 0.58 [72].

Depressive symptoms

Edinburgh Postnatal Depression Scale (EPDS) [8]

10-item self- report scale to screen for probable depression during the postnatal year in research and health care settings.

Range of scores 0 to 30

Standardised α 0.87; sensitivity 0.85 and specificity 0.77; positive predictive value 0.83[8].

Quality of relationship with intimate partner

Intimate Bonds Measure (IBM)

Subscales: Care, Control

Care subscale assesses sensitivity, warmth, emotional responsiveness, trust, physical gentleness and kindness.

Control subscale assesses coercion, dominance, exertion of power and extent of criticism.

Range of scores 0 to 36 for each subscale

Care: Cronbach's α 0.94; correlation with clinical interview ratings of quality of relationship 0.68.

Control: Cronbach's α 0.89 and correlation with clinical interview ratings of quality of relationship 0.74 [73].

Duration and frequency of infant crying and fussing in a 24 hour period

Barr Chart [74]

Possible range 0 to 24 hours

Parental diary of duration of episodes of crying, fussing, sleeping, and content infant behaviours.

Reliably completed by parents, high correlation with tape recordings: for frequency (r = 0.85, p = 0.002) and duration (r = 0.90, p = 0.001) of episodes [74].