Why does Britney Spears shave her head?

Britney Spears shaved her head as a tribute to her aunt who had died from cancer, according to a friend of the star.

The singer stunned the world when she cut off all her hair in full view of paparazzi camera crews at a Los Angeles salon in February 7.

She followed the stunt with a spell in rehab - but a pal claims Spears was suffering post-partum depression and grief and shaved off her hair as an act of "solidarity". The friend tells PageSix.com, "Britney's aunt had just died of cancer. She was feeling very guilty because she hadn't been there with her, she was overwhelmingly depressed and she shaved her head in solidarity."