A symptom complex including psychosis, delirium, hallucinations, and tremors (Mad Hatters Disease) is associated with exposure to which toxin?

• A. Arsenic
• B. Lead
• C. Mercury
• D. Cyanide

Answer: (C)

Mercury poisoning produces a neuropsychiatric syndrome called erethism, which includes personality changes, irritability, insomnia, memory problems, and, importantly, tremors, along with delirium and even hallucinations. Hatters in the past were exposed to mercury vapors during hat-making, giving rise to the name “Mad Hatters” disease. The tremors and the psychotic features described fit this mercury-related erethism pattern, because mercury readily crosses into the brain and disrupts neural function, leading to these characteristic CNS symptoms. The other toxins have different signature effects (for example, arsenic tends to cause GI and skin signs, lead more commonly causes cognitive and peripheral nerve issues without the classic erethism triad, and cyanide causes rapid collapse), so mercury is the toxin most closely linked to this symptom cluster.