Aripiprazole Added on for DMDD in Youths With ADHD

Inclusion Criteria: For subjects with comorbid ADHD and DMDD: * Subject meets the DSM-5 criteria for ADHD and DMDD * Subject is free from prior psychotropic medication for at least one year For subjects with ADHD only : * Subject meets the DSM-5 criteria for ADHD and DMDD * Subject is free from prior psychotropic medication for at least one year Exclusion Criteria: * Patients not willing to participate in the study after detailed explanation * Patients who could not follow the investigator's instructions * Patients with severe neurological or mental illness such as epileptic disorder, schizophrenia, bipolar disorder, mental retardation or uncontrolled suicide risk * Patients with severe medical illness or surgical conditions which were judged by investigators for safety concerns as inappropriate for this study, such as uncontrolled abnormal thyroid function, history of heart attack, uncontrolled hypertension. * Patients taking psychotropic medication within one year prior to the evaluation for entering our study * Patients being allergic to methylphenidate or aripiprazole * Female patients being pregnant, nursing, or lactating