Co-conditions
Autism is very rarely a "lone traveller", it quite often comes with one or more other conditions. Co-morbid conditions are other conditions which are strongly related to the first one. Many people use the words co-condition and co-morbid condition interchangeably but co-conditions aren't necessarily as related to the primary condition. The just happen to exist together. These days I usually use co-condition because you can't be sure how linked these conditions are.
Co-Conditions and Comorbids
Conditions which co-exist with autism are often less problematic than they would be if they existed purely on their own. For example, OCD under autism is often less "strict" than OCD by itself - of course, that's not always the case.
Some of the most common co-conditions are...
ADHD / ADD
Attention-Deficit Hyperactivity Disorder
Borderline Personality Disorder