What is a comorbid diagnosis? Comorbidity is one or more additional conditions existing at the same time with a primary condition. There are many common comorbid diagnoses that seem to relate to autism. Some of these conditions might be (but are not limited to): anxiety, epilepsy, gastrointestinal issues, ehlers-danlos syndrome, bipolar disorder, sensory processing disorder, sleep disorders, and vitamin deficiencies. The list goes on!