“…A total of 6 studies ( Carmassi et al, 2020 ; Dattoli et al, 2020 ; Korten et al, 2021 ; Lazzari et al, 2020 ; McBride et al, 2021 ; Tundo et al, 2021 ) were conducted in Europe, 4 studies ( Ackerman et al, 2020 , 2021 ; Wang et al, 2021 ; Yocum et al, 2021 ) in North America, 2 studies ( Uvais, 2020 ; Yin et al, 2020 ) in Asia, one study ( Karantonis et al, 2021 ) in Oceania, and one study included two different samples from independent geographical regions (Europe and Africa) ( Carta et al, 2021 ). Concerning study designs, 6 studies ( Ackerman et al, 2021 ; Carmassi et al, 2020 ; Dattoli et al, 2020 ; Karantonis et al, 2021 ; McBride et al, 2021 ; Tundo et al, 2021 ) were cross-sectional, 3 studies ( Carta et al, 2021 ; Korten et al, 2021 ; Yocum et al, 2021 ) were prospective cohort studies, one study( Ackerman et al, 2020 ) was a retrospective cohort study, and one study( Wang et al, 2021 ) was a case-control study, and 3 studies ( Lazzari et al, 2020 ; Uvais, 2020 ; Yin et al, 2020 ) were case reports/series. The diagnosis of BD was validated according to the DSM-5 by 8 studies( Ackerman et al, 2020 , 2021 ; Carmassi et al, 2020 ; Carta et al, 2021 ; Dattoli et al, 2020 ; Tundo et al, 2021 ; Uvais, 2020 ; Yin et al, 2020 ), the DSM-IV or DSM-IV-TR in 3 studies ( Karantonis et al, 2021 ; Korten et al, 2021 ; Yocum et al, 2021 ), and the ICD-10 in 3 studies ( Lazzari et al, 2020 ; McBride et al, 2021 ; Wang et al, 2021 ); additionally, the Mini-International Neuropsychiatric Interview (MINI) was adopted in 4 studies ( Ackerman et al, 2020 , 2021 ; Karantonis et al, 2021 ; Korten et al, 2021 ), and the Structured Clinical Interview for DSM-5 (SCID-5) was used in one st...…”