Using or abusing more than one substance can increase the risk of accidental overdose; actor Heath Ledger died in 2008 from taking a combination of drugs, reportedly for his chronic insomnia. The autopsy results indicated that he’d taken pain killers, several benzodiazepines (used to decrease anxiety), and an over-the-counter antihistamine that can induce drowsiness. He may have developed tolerance to standard doses of these medications; in combination, they caused his heart or breathing to slow down so much that he died (Falco, 2008).

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