A total of 5,009 public school teachers took sick leave due to mental illnesses such as depression during the 2015 academic year, according to a survey by the Ministry of Education, Culture, Sports, Science and Technology (MEXT).

The figure, accounting for 0.54 percent of the total number of teachers in Japan, represents a decrease of 36 compared to the 2014 academic year. But the trend of approximately 5,000 teachers taking mental illness-related sick leave each year since the 2007 academic year is continuing.

Altogether, 7,954 teachers took time off work due to any kind of illness during the 2015 academic year, with over 60 percent of these cases being due to mental illness, the survey found.

Mental illness-related sick leave occurred most frequently among teachers at special-needs schools, with 560 teachers, or 0.66 percent, at this type of school falling under this category. This was followed by 1,524, or 0.64 percent, of junior high school teachers; 2,237, or 0.55 percent, of elementary school teachers; 683, or 0.37 percent, of high school teachers; and five, or 0.3 percent, of secondary school teachers. Overall, 0.51% of all male teachers took mental illness-related sick leave, compared with 0.57% of all female teachers.

According to MEXT, "the busy work environment" is the main cause behind the high number of teachers taking mental-illness related sick leave each year. In a survey conducted by the Organization for Economic Cooperation and Development (OECD) in 2013, junior high school teachers in Japan worked an average of 53.9 hours per week -- which is notably higher than the mean of 38.3 hours per week across the 34 countries and regions that were surveyed. Factors such as lesson preparation, research regarding teaching materials, dealing with bullying and truancy, as well as involvement in extracurricular activities are leading to increased mental and physical exhaustion among teachers.

Rehabilitation support programs have been set up by some schools and local authorities to tackle this issue, but this has not had a major effect on the number of teachers taking sick leave. MEXT is working on ways to reduce long working hours in schools, such as by conducting surveys looking into club activities, and says it hopes to "decrease the number of sick leave cases due to mental illness by reducing the burden on teachers."

Meanwhile, the number of teachers who were punished or warned about indecent behavior such as indecent assault, prostitution or sexual harassment in the 2015 academic year reached a record high of 224 -- an increase of 19 teachers compared to the 2014 academic year. The percentage of victims who were pupils at the same school as the offending teacher was 40.7 percent.