Researchers say they have found a strong link between post-natal depression and breastfeeding duration, highlighting the need for more support for new mothers.

The pressure to breastfeed is impacting on the mental health of new mothers, a study suggests.

Research conducted by the Murdoch Childrens Research Institute in Melbourne has found women who reported depressive symptoms at three months after birth had significantly lower rates of breastfeeding at six months compared to women without depressive symptoms - 49 per cent versus 61 per cent.

The researchers suggest that women who have trouble breastfeeding may be more likely to develop post-natal depression and give up nursing their babies before the recommended six months.

Or it could be that women with maternal depression find it difficult to continue breastfeeding.

More than 1500 women were recruited from six public hospitals in early pregnancy (15 weeks gestation) and completed follow-up questionnaires at three and six months after the birth of their baby.

Almost 95 per cent of the new mothers initiated breastfeeding, 76 per cent were still breastfeeding at three months postpartum, and by six months this dropped to 61 per cent.

The differences in rates of breastfeeding between women who reported depressive symptoms and those who didn't started to emerge around three months post-birth, according to the data.

"We found significantly lower rates of breastfeeding at four, five and six months postpartum in women who had depressive symptoms at three months," said lead researcher, Dr Hannah Woolhouse.

Whether the depressive symptoms or the breastfeeding difficulties came first was too hard to determine, conceded Dr Woolhouse.

However the research does show a "strong and robust" association between maternal depression and breastfeeding duration.

"It could be that women experiencing depression is leading them to stop breastfeeding earlier, or it could be difficulty with breastfeeding is contributing to the beginning of post-natal depression," she said.

Reasons to wean a baby before six-months-old can be complex but research has shown that the most common reasons include nipple pain, low milk supply and latching difficulties.

The World Health Organisation recommends babies are breastfed exclusively to around six months of age, with the gradual introduction of appropriate solids and continued breastfeeding up to two years of age.

Experts from the Murdoch Institute say the new research highlights the need for more awareness and support for new mothers experiencing depression and breastfeeding difficulties.

"Women need to be compassionately supported in their infant-feeding choices whatever they are because the pressure on women around breastfeeding can potentially worsen their mental health," said Dr Woolhouse.

"The end goal should be women feeling confident and empowered."