Impact of COVID-19 pandemic on mental health of young people and adults: a systematic review protocol of observational studies - Silva Júnior, Fernando José Guedes da; Sales, Jaqueline Carvalho e Silva; Monteiro, Claudete Ferreira de Souza; Costa, Ana Paula Cardoso; Campos, Luana Ruth Braga; Miranda, Priscilla Ingrid Gomes; Monteiro, Thiago Alberto de Souza; Lima, Regina Aparecida Garcia de; Lopes Junior, Luis Carlos (BMJ Open, 2020)