Gwyneth Paltrow has opened up about her struggle with postpartum depression

The 'Iron Man' actress has revealed she struggled to cope for months after son Moses, now four, was born in April 2006.

Writing in her GOOP newsletter, Gwyneth – who also has a six-year-old daughter Apple with her husband, Coldplay frontman Chris Martin – admitted: "When my son, Moses, came into the world in 2006, I expected to have another period of euphoria following his birth, much the way I had when my daughter was born two years earlier. Instead I was confronted with one of the darkest and most painfully debilitating chapters of my life. For about five months I had, what I can see in hindsight as postnatal depression."

Gwyneth, 37, has previously revealed she suffered from the condition but only realised what was wrong with her once she had overcome it.

She said: "I didn't know I had it until after it was over. I just didn't know what was wrong with me. I felt really out of my body. I felt really disconnected. I felt really down. I felt pessimistic."

Postpartum depression – also known as postnatal depression - is caused by an imbalance of hormones in the body after a woman gives birth. Researchers have found that depression is one of the most common complications both during and after pregnancy.

In her GOOP newsletter, Gwyneth also included a piece written by 'The Twilight Saga: Eclipse' actress Bryce Dallas Howard, detailing her own battle with postpartum depression which caused her to refer to her newborn son Theo as "it".

Bryce said: "It is strange for me to recall what I was like at that time. I seemed to be suffering emotional amnesia. I couldn't genuinely cry, or laugh, or be moved by anything."