Five patients with symptoms of persistent sleepiness were described in detail in 1925 by Willi Kleine, a neurologist from Frankfurt. This report was followed four years later by details of a similar case by New York-based psychiatrist Max Levin. In 1935, Levin published information about several more cases, including one described by Kleine. Levin noted that some patients displayed an intense appetite in addition to their persistent tiredness. MacDonald Critchley, who first wrote about the condition in 1942, described 11 cases he had examined and reviewed 15 other published cases in a 1962 publication. In the report, which included patients he had examined in the Royal Navy during World War II, he observed that irritability and depersonalization often occurred while patients were awake. He named the condition Kleine–Levin syndrome and noted four common traits: hypersexuality, adolescent onset, spontaneous resolution, and compulsive eating. He believed that the condition only affected males, but later studies showed some female patients. In the 1970s, several psychoanalytic and psychodynamic explanations for the condition were proposed. In 1980, a Hawaiian–Caucasian family was found in which nine family members suffered from the condition.