Mental illness is an umbrella term for a wide range of ailments. However, the top three major mental illnesses in the country are schizophrenia, Alzheimer's disease and depression.

"Because of the expensive medical fees, most of the city's mental patients take medicine only when they fall ill," Ning said.

Zhou Yongdi, director of the president's office of Guangzhou Baiyun district hospital of mental diseases, said medical fees for treating tumors and cardiovascular diseases actually cannot be compared with those for treating mental illnesses, despite patients incurring expensive surgical charges, because it usually takes a long time to treat mental illness.

"Electric shock therapy, which is sometimes used to treat mental illness, costs about 3,000 yuan ($439) for a single application," Zhou said.

That is equal to the monthly income of a local worker, he added.

A Guangzhou resident, surnamed Liang, said he has become heavily in debt since his daughter was diagnosed with a mental illness three years ago.

"A course of treatment that only lasts a month costs about 10,000 yuan," said Liang, who now has to seek financial support from the local government to continue his daughter's treatment.

The increasing number of people with mental illnesses has raised concern on both sides of the medical divide.

While some who suffer from mental illness are locked up at home by their families, most people afflicted by mental illness are able to freely stroll about in local communities and on streets, which occasionally poses a threat to the public, Ning said.

Some of the city's injury and even homicide cases have been reported as havn't been caused by people suffering from mental illness.

Chen Yunqi, a local white-collar worker, said the relevant government departments of health and civil affairs should do more to help the large number of people with mental illness.

"It is not good news that many mentally ill people stroll in the city's public spaces and on its streets. They not only threaten public security, but also damage the city's image," he said.