Chinese children spend too much time studying and not enough on activities that develop their social skills, which could affect their ability to forge personal and professional relationships as adults, research shows.

A study by the China National Children's Center found that while 48 percent of youngsters attend cram sessions after school, more than half say they rarely have time to play with friends.

The Blue Book of Children: The Annual Report on Children's Participation 2017, which was released on Thursday, also found almost a third of primary school children spend more than two hours on homework on school days, twice the maximum time recommended for that age group by the Ministry of Education.

The findings are based on a yearlong study beginning in September 2016 of 8,847 children in fifth grade and above. Respondents were spread across urban and rural areas in seven cities, including Beijing, Harbin and Guiyang.

The center said the large number of hours spent studying has made children's participation in extracurricular activities "inadequate", with 68 percent having never participated in activities unrelated to school and study. More than 14 percent reported they've never even talked with their next-door neighbors.

Study also dominates parent-child interactions. More than 90 percent of respondents said their conversations with parents focus on school performance, whereas one-third reported their parents never talk about their job and more than 25 percent never talk about how to manage money, it said.

Rana Flowers, China's representative to UNICEF, stressed the importance of children's participation in aspects other than just school, which help cultivate children's skills such as teamwork, communication and analyzing and solving problems.

"Children do not suddenly become responsible, participating adults at the age of 18 or 21," she said. "Without these, the children of today will not succeed in the jobs of tomorrow."

Other statistics also shed light on the academic pressure of Chinese schoolchildren.

According to a 2015 survey conducted by Afanti－an online learning app－nearly half of school-age children in China spent an average of three hours on homework each day, four times of their counterparts in Japan and six times those in South Korea.