71 Assessing medical decision-making competence in transgender minors 4 DISCUSSION The current study revealed that 93.2% and 89.2% of the transgender adolescents who were about to start PS and were participating in this study were competent to give IC on the basis of the standard clinical assessment and when using the MacCAT-T interview, respectively. This is a reassuring finding, which reveals that guidelines that require understanding the pros and cons of the treatment and capacity for IC for starting PS are followed for these participants (Coleman et al., 2012; Hembree et al., 2017). This study was performed after several sessions with adolescents and parents aimed at obtaining understanding of the consequences of PS, including not only the short-term, with regard to suppression of further feminization or virilization, but also long-term considerations of bone development, surgical options, and fertility (Di Ceglie, 2018). This study further looked into several variables potentially associated with MDC. Of the examined variables, higher full-scale intelligence quotient (IQ) and sex (birth-assigned girls) were associated with higher MacCAT-T scores. The association of a higher intelligence with MDC is in line with other research (Hein et al., 2015c; Miller, Drotar, & Kodish, 2004). The birth-assigned girls in our study might have had a more advanced puberty compared with the birth-assigned boys, which might be related to a deeper understanding of the consequences of PS (Koerselman & Pekkarinen, 2017). Contrary to our expectations and earlier research, age was not correlated to MacCAT-T scores in this study. Although the participants seem like a representative sample, it may be too homogeneous, with regard to age, to detect a significant effect because the sample included few participants aged ≤11 years. Most research suggests that MDC is reached little before the age of 12 years (Billick et al., 1998; Hein et al., 2014; Mårtenson & Fägerskiöld, 2008). Finally, no association between MDC and duration of the diagnostic trajectory, and between MDC and behavioural and/ or emotional difficulties was found. This finding was also against our expectation because psychological difficulties can interfere with MDC. However, one of the criteria for starting PS applied at the Dutch gender identity clinics is ‘having no interfering psychosocial difficulties’ (Coleman et al., 2012; Hembree et al., 2017). Therefore, by protocol, adolescents with severe psychosocial difficulties might have been referred for appropriate treatment before deciding on PS. The results of this study confirm the feasibility of the Dutch version of the MacCAT-T for children and adolescents in assessing transgender adolescents’ MDC; the interrater agreement of the reference standard and MacCAT-T-based judgements were both high (respectively, 89.2% and 86.5%). Furthermore, the results of this study offer first indications of validity of the MacCAT-T for judging transgender adolescents’ MDC (intermethod agreement was 87.8%), and the MacCAT-T could therefore be used in clinical practice when MDC assessment is difficult. The MacCAT-T should not necessarily replace (a part