Rattan, a middle-aged man is chronically preoccupied with his health. For many years he feared that his irregular bowel functions meant he had cancer. Now he is very preoccupied about having a serious hea disease, despite his physician's assurance that the occasional "extra beats" he detects when he checks his pulse are completely benign. What is his most likely diagnosis?
Somatization disorder Hypochondriasis Delusional disorder Pain disorder