Individuals with autism may experience medical conditions and behavioral issues in addition to ASD. These conditions, known as "co-morbid" conditions, may include depressions, epilepsy, sleep disturbances, gastrointestinal (GI) problems, and anxiety.
According to research estimates, at least 30% of people with autism also have an anxiety disorder. Anxiety disorders co-morbid with autism may include phobias (including social phobia), separation anxiety, excessive worry, and obsessive compulsive disorder. As would be the case with anyone experiencing these issues, anxiety can be very difficult to manage for a person with autism.
Some research also indicates that adolescents and individuals who are "higher-functioning" on the spectrum may experience higher rates of anxiety disorders.
Among people on the spectrum, rates of anxiety can range from mild/occasional to severe enough to cause difficulty with daily functioning.
Autism Speaks: Treatments for Associated Medical Conditions - http://www.autismspeaks.org/what-autism/treatment/treatment-associated-medical-conditions
Autism Speaks: Treatment for Associated Psychiatric Conditions - http://www.autismspeaks.org/what-autism/treatment/treatment-associated-psychiatric-conditions