Stereotypic movement disorder (SMD) is a motor disorder with onset in childhood involving restrictive and/or repetitive, nonfunctional motor behavior (e.g., hand waving or head banging), that markedly interferes with normal activities or results in bodily injury.

[1] To be classified as SMD, the behavior in question must not be due to the direct effects of a substance, autism, or another medical condition.

[2] Common repetitive movements of SMD include head banging, arm waving, hand shaking, rocking and rhythmic movements, self-biting, self-hitting, and skin-picking;[1] other stereotypies are thumb-sucking, dermatophagia, nail biting, trichotillomania, bruxism and abnormal running or skipping.

SMD may occur with Lesch–Nyhan syndrome, intellectual disability, Autistic Spectrum Disorder, fetal alcohol exposure, or as a result of amphetamine intoxication.

[1] Stereotypic movement disorder is often misdiagnosed as tics or Tourette syndrome (TS).