Hong Kong (CNN)More than 1 in 5 sailors on Chinese submarines operating in the South China Sea reported mental health problems, according to a new study that provides a rare insight into the inner workings of one of the Chinese military's most guarded assets.
Chinese submarine sailors report significant mental health problems in rare study
The research by China's Second Military Medical University and Navy Military Medical University, published in the British journal Military Medicine, showed submariners reported severe psychological problems at much higher rates compared to People's Liberation Army (PLA) forces as a whole.
"This study demonstrates for the first time that soldiers and officers in the submarine force in the South China Sea are facing mental health risks and suffering from serious psychological problems," the researchers concluded.
The study surveyed 580 male submariners in the PLA Navy's South China Sea fleet, with 511 of those returning complete responses. While the overall condition of submariners' mental health was only slightly worse than PLA troops in general, the research showed significantly worse problems among the sub force in four areas.
PLA Navy submariners showed higher rates of anxiety, phobias, paranoia and somatization -- where mental issues surface with physical symptoms -- than among Chinese troops overall, the study found.
Conditions and the military situation in the South China Sea exacerbate the problems, the researchers said.
The South China Sea has become a hotspot for military tensions in recent years.
Beijing claims almost all of the 1.3 million square mile South China Sea, and since 2014 it has built up tiny reefs and sandbars into man-made artificial islands, fortified with missiles, runways and weapons systems -- antagonizing regional governments with overlapping claims.
Washington doesn't recognize those claims and regularly sends US warships and military aircraft through the region.
China in response has increased military maneuvers in the region, which means submarines can spend two to three months submerged in tight, noisy confines that lead to sleep deprivation among submariners, the researchers said.
"The physically unfriendly environment means that submariners are not only living in an isolated, constantly closed environment, but they also sleep in a cabin that is exposed to excessive noise," the study said.
Constant exposure to artificial light can also lead to mental problems, the researchers said.
The researchers found submariners with college or post-graduate degrees suffered more mental problems than those with lower levels of education. They suggested two reasons for this: The highly educated have no way to relieve psychological pressures in their isolated environment and long for "freedom and integration into society."
The researchers also said the problems were more pronounced among those on nuclear-powered submarines versus those that were conventionally powered. Not only do complex nuclear-powered submarines require better educated personnel, those aboard them tend to worry more about accidents and the effect of radiation on their health, the researchers said.
Although the mental health of submariners has been explored in Western navies, the researchers said few studies have been published from non-English speaking countries.