Pharmacogenomics of Stimulant Treatment Response

Who May Qualify: Patients will be eligible for participation if all the following are true. - Aged 6 - 24 years. - Located in Western Canada (i.e., Alberta, British Columbia, Saskatchewan, Manitoba). - Primary diagnosis of ADHD (all types). - Starting Methylphenidate (excluding immediate release forms) treatment. Who Should NOT Join This Trial: Patients will be excluded from participation if any of the following are true. - Co-occurring psychotic, bipolar or eating disorders. - Significant risk of suicide. - An intellectual disability, or diagnosis of autism spectrum disorder (ASD) or tics/Tourette disorders. - Past 12-month high-risk alcohol or substance use defined as monthly or more frequent use. - Psychotherapy or brain stimulation-based therapy initiated within 8 weeks of referral or plans to initiate/change these types of therapies during the study - History of liver or bone marrow (hematopoietic cell) transplant as these events can result in ambiguous genomic results. Always talk to your doctor about whether this trial is right for you.