The most common form of postnatal disturbance is a mild transient disturbance termed the 'baby blues', suffered by over half the population of newly delivered western mothers during the first week to ten days following birth. One study found that 25% of women admitted within three months of delivery had consulted for psychological symptoms during pregnancy and almost 50% had had symptoms of anxiety or depression during pregnancy. Patients with an early onset of affective or cycloid psychosis have been found, in a prospective study, to be more suspicious, tense, anxious excited during late pregnancy when interviewed by midwives without psychiatric training. The inner experience of a woman suffering from psychosis is so strange and unlike what most of people experience that it is very difficult for carers to imagine what the sufferer is going through internally. Clinical depression experienced postnatally has been attributed to a variety of aetiological factors ranging from the biochemical to the psychological.