Final answer:
Comorbidity in the DSM-V context is often attributed to the presence of overlapping symptoms between disorders, rendering distinct diagnoses challenging and potentially leading to multiple concurrent disorder diagnoses.
Step-by-step explanation:
The occurrence of comorbidity among disorders according to DSM-V primarily involves the aspect of option b: overlapping symptoms.
Comorbidity refers to the presence of more than one disorder in a person at the same time. The DSM-V, which is a manual used for the classification of mental disorders, acknowledges that diagnostic categories may not always reflect separate and distinct disorders due to overlapping symptoms which can lead to the diagnosis of multiple disorders. These overlapping symptoms can create a clinical picture where disorders appear to co-occur, thus contributing to comorbidity. Complex interactions between psychological, biological, and social factors could all play a role in the manifest pattern of comorbidity among different disorders.