The study purpose is to analyze changes in the mental health structure and its disorders among students who receive online education. The research involved 23 students (6 boys and 17 girls, average age 18 years). The study covers the period from October 2019 to September 2020. The participating students underwent the assessment using a Telegram before and after quarantine when they studied under the conventional full-time program. Additionally, they were tested during the lockdown due to the COVID-19 when they received online training. The results showed that study participants did not experience stress, depression, or anxiety before switching to online training. However, shifting to online learning mode, students under study experienced an increase in the stress level by 55.4%. Moreover, the study also showed that the stress level among students increased after returning from online to full-time training. However, the indicators had a lesser extent (by 40.2%, p = 0.0031). During online training, the number of students who did not experience stress and students with a mild stress level decreased. Meantime, students who faced stress reactions increased four times (p = 0.029). However, the study did not indicate any significant changes in anxiety levels among students.