fatigue and depressive symptoms are common among women in the postpartum period, and it has been proposed that fatigue is a risk factor for later depression. To progress this research, there is a need to clarify the conceptual and measurement issue of whether these two sets of symptoms are distinct constructs. There is also a need to determine whether they are distinct constructs beyond the postnatal period. The aim of the study was to assess the construct and discriminant validity of fatigue and depressive symptoms as measured by the SF-36 Vitality subscale (SF-36) and the Edinburgh Postnatal Depression Scale (EPDS) at six months and at four years post partum.data from over 1000 women participating in the Maternal Health Study, a longitudinal study of women׳s physical and psychological health and recovery after childbirth were used.confirmatory factor analysis revealed a two-factor model of fatigue and depressive symptoms represented as distinct but related constructs was a better fit to the data than a one-factor model of fatigue and depression sharing the same underlying construct at both six months and four years post partum.this study provides empirical evidence that maternal fatigue and depression in the first year after having a baby and at four years post partum are best understood as separate psychological constructs or experiences. The findings have important implications for clinical practice, in particular underlining the importance of differentiating tiredness from depression.