A 24-year-old man presents with a two-year history of fatigue, malaise, daytime sleepiness, and poor appetite. No other symptoms are present.

He sought medical attention three times over this period. As no physical signs were found, and all basic investigations including complete blood counts, electrolyte counts, and renal and liver profiles were normal, his symptoms were considered to be either psychogenic or factitious.

He does not smoke, drinks around 5 to 7 units of alcohol per week, and "occasionally" uses marijuana. He denies using "hard" drugs. A electrolyte assay reveals a serum sodium of 135 mEq/L (normal: 135-145). A complete blood count, liver profile, and renal profile are all within normal parameters.