RESUMEN
INTRODUCTION: The COVID-19 pandemic has been particularly difficult for populations at risk for mental health problems, such as healthcare professionals and medical students. In the present study, we evaluated the effect of the pandemic on mental health in a sample of Mexican medical students with and without a mental health diagnosis. METHOD: Longitudinal and descriptive study based on scales of suicidal ideation, depressive symptoms and risk of alcohol consumption, conducted in April and December 2020. RESULTS: Sample includes 247 medical students, 64.4% are women. Prevalence of depression increased between April and December from 19.84% to 40.08%. In the case of women from 23.67% to 42.60% (χ2 = 0.000) and in men from 11.54% to 34.62% (χ2 = 0.001). In April 16.92% of healthy students presented some sign of depression and in December the percentage increased to 40.80% (χ2 = 0.000). Regarding medicated students, the prevalence in April was 32.61% and in December it was 36.96% (χ2 = 0.662). In April, the medicated students with risk of suicidal ideation were 17 out of 46 (36.96%), compared to the students without a diagnosis of psychiatric illness were 29 out of 201 (13.43%) (χ2 = 0.000). For December, the non-medicated students at risk of suicidal ideation were 34 out of 201 (16.91%), and the medicated students were 12 out of 46 (26.09%) (χ2 = 0.149). CONCLUSIONS: The pandemic has increase the rate of depression in medical students, being more severe in women. Students under psychiatric treatment showed a higher prevalence of depression; however, the fact of being under treatment resulted in a protective factor for the increase in the prevalence of depression. It is important to deepen the understanding of the causes of depression and to disseminate among the university community the benefits of early detection and treatment of people with socio-emotional disorders.