• GHQ;
  • high-school students;
  • psychotic-like experiences (PLEs);
  • sleep;
  • twin


Aim: Studying what factors and behaviours to work on may be a key to develop the effective prevention of future mental disorder in both high-risk and general young subjects. This study aimed to investigate whether twins are more vulnerable to mental health problems including psychotic-like experiences (PLEs) than singletons and what factors on lifestyle and social environment are associated with poor mental health.

Methods: Subjects comprised 341 Japanese high-school students (173 males and 168 females) including 62 twins. We examined PLEs, general psychological distress, length and regularity of sleep, domestic violence, being bullied and other environmental factors using questionnaires including the 12-item General Health Questionnaire (GHQ-12). The variables were compared between twins and singletons. Whether variables on lifestyle and social environment affect PLEs and GHQ-12 scores were studied by logistic regression.

Results: Significant difference was observed in PLEs and GHQ-12 between twins and singletons. Experiencing PLEs was negatively associated with being a twin (OR = 0.293, 95% CI = 0.101–0.847) and length of sleep (OR = 0.685, 95% CI = 0.519–0.903). GHQ-12 > 4 was significantly associated with irregular sleep schedule (OR = 3.042, 95% CI = 1.818–5.090), being bullied (OR = 3.677, 95% CI = 1.317–10.266) and having no people to confide in (OR = 2.615, 95% CI = 1.249–5.475).

Conclusion: Poor mental health status including experiencing PLEs might be less frequent in twins than in singletons. Problems in sleep length, its schedule and human relationships were significantly associated with mental health in high-school students as we hypothesized. Early identification programmes and mental health education focused on these factors may be helpful.