- NA (Narcotics Anonymous)
- Nabilone
- Nalmafene
- Naloxone
- Naltrexone
- Nar-Anon
- Narcissistic personality disorder
- Narcolepsy
- Narcotic
- Narcotic withdrawal syndrome
- Narrative therapy
- Narvox
- National Alliance on Mental Illness
- National Institute of Mental Health
- National Institute on Alcohol Abuse and Alcoholism
- National Institutes of Health
- National Organization on Fetal Alcohol Syndrome
- National Suicide Prevention Lifeline
- National Survey on Drug Use and Health
- Negative reinforcement
- Nembutal
- Neuroactive peptides
- Neurobiological disorder
- Neurofeedback
- Neurological brain disorder
- Neurontin
- Neuropeptide Y
- Neurotransmitters
- Nicotine
- Nicotine addiction
- Nicotine Anonymous (NicA)
- Night eating syndrome
- Niravam
- Nitrous oxide
- Norepinephrine
- NUCYNTA
- Numorphan