Mental health of children and adolescents with pre-existing psychiatric and developmental disorders during the first pandemic-related lockdown: A cross-sectional study in Greece oleh K. Magklara, I. Giannopoulou, K. Kotsis, E. Tsalamanios, A. Grigoriadou, K. Ladopoulou, I. Koullourou, A. Serdari, N. Sadeghi, G. O'Callaghan, D. Priftis, C. Ntakolia, A. Stringaris, E. Lazaratou, E. Lagakou, E. Mamaki, E. Neou, O. Polaki, G. Triantafyllou, E. Valvi, V. Vassara