Confinement was a helpful measure to avoid virus propagation, but social isolation and the massive closure of face-to face activities in educational institutions, impacted negatively in mental health of students, it increased stress and anxiety in adolescents, affecting their communication skills in this significant step of interpersonal relationships, and the search for their identity. The lockdown in addition to stress and anxiety triggered fear emotions, frustration, worrying and anger, as well as changes in driving energy, diminishing interest and desires. This work aimed to analyze the impact on mental health in first year secondary school adolescents after the COVID-19 pandemic lockdown. Method: Qualitative and phenomenological research, 25 students of first year from a public secondary school of Mexico's metropolitan area participated in the study; they were girls and boys 12 -13 years old. Data collection was through a semi-structured interview, testimonials and anecdotes, in two hour sessions, along a week; research team recorded the interviews, testimonials and anecdotes. A signed informed consent was obtained from school authorities, parents and the assent of students. Obtained qualitative data were analyzed according to De Souza Minayo. Results: Four categories emerged with sub-categories. Category 1: Anxiety crisis, sub-categories 1.1.