While studies have reported effects on digital media during the COVID-19 restrictions, few have included data prior to the pandemic, and most have only measured screen time. We therefore investigated changes in specific digital media activities, as well as mental health and lifestyle habits, in a longitudinal study of adolescents spanning from before the pandemic (T1) to one month into restrictions (T2) and one year later when schools had reopened (T3). Adolescents (16–19 years) rated smartphone use, problematic/addictive media use, negative experiences (e.g., victimization), mental health (i.e., irritability, stress, and closeness), and protective lifestyle habits (i.e., sleep and exercise). Results showed initial decreases in irritability and negative digital experiences, increases in sleep and exercise, as well as a decrease in closeness during remote learning (T2). However, these changes returned to, or superseded, their initial levels at follow-up (T3). There were also increases in digital media use and stress at T3. Conclusively, by investigating specific digital media activities and collecting data both prior to and during different phases of the pandemic, we were able to find both positive and negative effects.