84 Neurodevelopmental Disorders
Gender-Related Diagnostic Issues
Males are more commonly affected than females,  but there are no gender differences in the
kinds of tics, age at onset, or course. Wome n with persistent tic disorders may be more
likely to experience anxiety and depression.
Functional Consequenc es of Tic Disorders
Many individuals with mild to moderate tic se verity experience no distress or impairment
in functioning and may even be unaware of their tics. Individuals with more severe symp-
toms generally have more impairment in daily living, but ev en individuals with moderate
or even severe tic disorders may function we ll. The presence of a co-occurring condition,
such as ADHD or OCD, can have greater impa ct on functioning. Less commonly, tics dis-
rupt functioning in daily activities and result in social isolation, interpersonal conflict,
peer victimization, inab ility to work or to go to school, and lower quality of life. The indi-
vidual also may experience substantial psycho logical distress. Rare complications of Tou-
rette’s disorder include physical injury, such as  eye injury (from hitting oneself in the face),
and orthopedic and neurological injury (e.g., disc disease related to forceful head and neck
movements).
Differential Diagnosis
Abnormal movements that may accompany other medical conditions and stereotypic
movement disorder. Motor stereotypies  are defined as involuntary rhythmic, repetitive,
predictable movements that appe ar purposeful but serve no obvious adaptive function or
purpose and stop with distraction. Examples  include repetitive hand waving/rotating,
arm flapping, and finger wiggling. Motor stereo typies can be differentiated from tics based
on the former’s earlier age at onset (younger than 3 years), prolonged duration (seconds to