Medical research has shown that chronic fatigue syndrome is definitely not the product of mental or emotional disorders, but is instead completely caused either by immunologic or genetic factors. Yet, other medical research has found that a large percentage of patients treated for chronic fatigue syndrome are also treated for depression and anxiety. Which one of the following, if true, helps explain the information presented above? ['Patients with chronic medical conditions often subsequently develop depression and anxiety.', 'People with depression are often unaware that they have other medical problems that require professional treatment.', 'Most people with chronic fatigue syndrome believe that their condition is caused by immunologic rather than genetic factors.', 'Patients are often unaware that they suffer from depression and anxiety.']