The short answer is that elevated omega-6 intakes are associated with an increase in all inflammatory diseases-which is to say virtually all diseases. The list includes (but isn't limited to):
Cardiovascular disease: The relationship between intake n-6 fats and cardiovascular mortality is particularly strikingType 2 diabetesObesityMetabolic syndromeIrritable bowel syndrome & inflammatory bowel diseaseMacular degenerationRheumatoid arthritisAsthmaCancerPsychiatric disordersAutoimmune diseases