The purpose of this clinical trial is learn whether a behavioral (non-medication) treatment can reduce nightmares in adults with Rapid Eye Movement (REM) Sleep Behavior Disorder (RBD). People with RBD will be enrolled in the study along with their family members (a partner or other family member residing in the same home). All participants will receive the treatment via videoconference and will complete 2 assessments. Participants with RBD will attend 7 sessions, and their family members will attend 2 of those sessions with them.

Inclusion Criteria:

• Diagnosis of isolated RBD or RBD secondary to neurodegenerative disease
• Age 18 or older
• Speak, read, and write English
• Live in the United States
• Nightmare frequency ≥3 times per week
• Disturbing Dream and Nightmare Severity Index score indicative of nightmare disorder
• Sleep, neurological, and psychiatric medications stable for at least 1 month and willing to keep medications stable through the course of the study
• Live with a family member who is willing to participate in the study

Exclusion Criteria:

• Possible dementia
• Narcolepsy
• Posttraumatic stress disorder
• Previous behavioral treatment for nightmares
• Currently engaged in sleep- or trauma-focused psychotherapy
• Taking a medication that could cause RBD, if the medication was started prior to onset of RBD symptoms

Inclusion Criteria (Family Members):

• Live with a family member who meets all of the above criteria
• Age 18 or older
• Speak, read, and write English
• Live in the United States