Shanghai - The police began judicial appraisal on Monday of the mental state of a Chinese student who stabbed his mother after flying to Shanghai from Japan.

The 25-year-old man, surnamed Wang, is accused of stabbing his mother nine times when he arrived at Pudong International Airport on April 1, just 10 minutes after his mother had picked him up. Wang was detained at the scene of the alleged crime, according to the Shanghai police.

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The 52-year-old mother, surnamed Gu, survived the attack and a subsequent coma. She was transferred from an intensive care unit to a regular ward at a local hospital on Monday.

Gu said her son, a student in Japan for the past five years, had been suffering from mental disorders before the attack occurred.

The student's aunt said relatives saw him exhibit unusual behaviors in recent months. He, for instance, would suddenly burst into laughter after being sad. And his mental situation only became worse after a large earthquake struck Japan in March, according to Xinmin.com, a news website in Shanghai.

The mother said she suspected that her son experienced auditory hallucinations. He often told her that he believed someone had been speaking to him at times when, in fact, he had been completely alone, reported Shanghai-based Oriental Morning Post.

The student told the police that he became irritated when his mother met him at the airport and began nagging him. So he took out a knife in his luggage and stabbed her. He said his mind went blank when the attack began, according to the police.

The police said they have not yet determined the motive behind the stabbing.

Meanwhile, an increasing amount of attention is being paid to the mental health of students going to school abroad, especially after several of them were implicated in violent crimes in recent days.

A Chinese student attending school in Sweden is accused of killing his 25-year-old fellow student, Chen Hao, a woman from Shanghai, on March 31. Chen was stabbed more than 10 times while she was on shopping trip.

Before the attack, Chen had told her close friend that the suspect, whose name hasn't been released, had asked her to be his girlfriend and that she had turned him down, according to Oriental Morning Post.

Fang Ying, manager of the UK education department at the Shanghai CIIC Education International Co, said many students aren't prepared for the hardships that come with going to school in a foreign country.

"Many parents thought an overseas education could make their children stronger competitors in the future, and that the earlier their children went abroad, the easier it would be for them to get accustomed to life overseas," she said.

"But going alone to study is not good for every student, especially at a young age."

"Many Chinese children are spoiled by their parents, who tend to be very protective. They often feel lonely and depressed when they first come to a foreign land," Fang said. "Parents should pay more attention to their children's mental health when they are abroad. If proper remedies aren't taken, a child's personal development will be hindered."