A 10-year-old girl suffered from headaches, vomiting and low spirits for more than a month - all because of the birth of her younger brother, Yangtze Evening News reported.

Second-grader Xiaojin (an alias) in Huzhou City of Zhejiang Province used to be happy and active, enjoyed good academic scores, and also served as the class monitor.

About a month ago, she seemed to suddenly fall ill and was always gloomy. The parents brought her to several local hospitals but failed to find a reason.

Suspecting the daughter may have caught encephalitis, an inflammation of the brain with similar symptoms, the worried parents then brought her to the Second Affiliated Hospital of Zhejiang University School of Medicine for treatment.

Medical checks excluded encephalitis and doctors finally determined the girl's symptoms are the result of a sibling rivalry disorder.

The parents were thought to give too much attention to their baby son, born about six months ago, and neglected their daughter's needs.

Doctors at the hospital suggested it is better for parents to talk with their first child about birth plans and not to overestimate the child's abilities of adjusting to a new family.

Sibling rivalry disorder can occur when children show some degree of emotional disturbance following the birth of a younger sibling, said experts.