Chloë Grace Moretz as Susannah Cahalan

Thomas Mann as Stephen Grywalski

Richard Armitage as Tom Cahalan

Carrie-Anne Moss as Rhona Nack

Jenny Slate as Margo

Tyler Perry as Richard

Alex Zahara as Allen

Jenn MacLean-Angus as Giselle

Ken Tremblett as Senator

Navid Negahban as Dr. Najjar

Robert Moloney as Dr. Ryan

Agam Darshi as Dr. Khan

Janet Kidder as Dr. Siskin

Vincent Gail as Dr. Samson

Daniel Bacon as Dr. Han

Alison Araya as EEG Tech

Brian McCaig as Intern

Elizabeth Bowen as Publicist

Nicole LaPlaca as Young Nurse

Lindsay Navarro as Young Waitress

Jessie Fraser as Woman

Lee Majdoub as Guy