ADHD symptoms were measured using the World Health Organization adult ADHD self-report scale (ASRS) (Kessler et al., 2005). ASRS consists of 18 items, nine measuring symptoms of inattention and nine measuring symptoms of hyperactivity impulsivity. Symptoms are rated on a 5-point Likert scale ranging from ‘never’ to ‘very often’. The ASRS has shown high internal consistency and validity in use with adolescents (Adler et al., 2012). The Cronbach's alpha of the ASRS in the current study was 0.91.