Neurocognitive Mechanisms Underlying Smartphone-Assisted Prevention of Relapse in Opioid Use Disorder

Inclusion Criteria: * Sex: male or female * Age: 18 years and older * (MRI sub-study): Age: 18-50 years old * In Phase I treatment of MAT for opioid-use disorder. (Phase I indicates that patient is receiving no more than one week of take-home medications at each weekly clinic visit.) * Must be willing to use a smartphone if randomized to the smartphone intervention arm * (MRI sub-study): Native English-speaking Exclusion Criteria: * (MRI) Medical history: A history of neurological, cardiovascular, or infectious disease would exclude study participation. A loss of consciousness of 20 or more min or other evidence of brain trauma also would be exclusionary. * (MRI) Pregnancy: A positive test for pregnancy prior to fMRI would exclude participation, due to unknown effect of high-field MRI on developing fetus. * (MRI) MRI contraindications: Exclusion criteria for MRI include (1) the presence of non-removable internal (e.g., cardiac pacemakers, aneurysm clips, artificial joints) or external (e.g., piercings, orthodontics) ferromagnetic objects; (2) claustrophobia in a confined MRI environment; (3) medications that interfere with hemodynamic coupling (e.g., beta blockers); (4) hypersensitivity to loud noise; or (5) a body circumference exceeding 60cm due to broad shoulders or morbid obesity