- Imago relationship therapy
- Inhalants
- Internet addiction
- Interpersonal therapy
- Intervention
- Idiosyncratic intoxication
- Ignition interlocks
- Iophen C-NR
- Intermittent explosive disorder
- Intensive outpatient treatment
- Inpatient rehab
- Insufflated
- Insulin
- Ionamin
- Interventionist
- Intoxication
- Impulse control disorder
- Impulsive behavior
- Insufflated
- Interpersonal and social rhythm therapy for bipolar disorder
- Integrative behavioral couples therapy