"Throughout my teenage years, I was very insecure," she told the magazine Oslo/Norway. "I wondered what was right for me to say. If someone criticized me, I took it very much to heart. I felt very guilty about feeling depressed when I am so privileged,"
Princess Märtha Louise is the only daughter of King Harald and Crown Princess Sonia, and fourth in line to the Norwegian throne.
She would have been first in line, if a 1990 change to Norway's law of succession had applied retroactively to include those born before that year.
She works as a folk singer, children's author, and alternative medical practitioner, and caused a furore in 2007 when she launched Astarte Inspiration, a centre aimed at teaching people how to communicate with angels.
Märtha Louise claims that she realised as a child that she could read people's inner feelings and communicate with heavenly beings.
"It was while I was taking care of the horses that I got in contact with the angels," she wrote on the centre's website. "I have lately understood the value of this important gift and I wish to share it with other people, maybe with you."
The princess moved to London in September 2012 with her husband, the Norwegian novelist and playwright Ari Behn.