There is clear evidence that China's tens of millions of stay-at-home children in rural areas suffer psychologically due to the absence of their parents. But recent studies show that urban children also experience depression, mostly because a psychological distance exists between them and their parents, despite being physically closer.

The Wuhan Hospital for Psychotherapy in Hubei province treated 207 child patients from July 2014 to April 2015. Half of them were left-behind children, and half of those were urban patients. The percentage is unusually high, considering that the overall number of China's left-behind rural children, at 61 million, is very large.

A child is defined by doctors as being "left behind" if one or both of the parents is unable to take care of their child because of work obligations. This is not a phenomenon specific to rural areas. In cities, many busy parents choose to leave their children in the care of grandparents, and only visit them every week or month. These are the so-called "invisible" left-behind children.

The Wuhan Mental Health Center conducted a survey of 3,000 children aged 6 to 14, and found that approximately 14 percent of left-behind children have mental health issues.

The findings show that even in well-off urban households, the absence of parents poses serious problems. Left-behind children often suffer from a sense of insecurity, and their mental problems can lead to physical symptoms.

Overindulgence by grandparents can also hamper children from becoming independent and confident, potentially turning them into overbearing and selfish troublemakers.

A father plays a very important role in a family, but for "invisible" left-behind children, the absence of a father is very common, as men are more likely to be the breadwinners while the mothers stay home. But children, especially boys, who grow up without a father figure tend to be more sensitive and narrow-minded — and more likely to experience anxiety and depression.

Running away from home is also common among left-behind children.

Interaction with parents helps facilitate the development of a child's gender identity, social adaptation, learning behavior and emotional intelligence. Many parents only pay attention to a child's academic development, ignoring their emotional needs. Children growing up in such an environment may not open up to their parents, let alone listen to their advice.