Final answer:
The Egyptians and Greeks believed mental illness was caused by miasma, and used strong smells to combat the perceived toxic vapors. These ancient cultures also incorporated religious and supernatural concepts into their health practices. Modern biochemical theories explaining mental illness in terms of neurotransmitters emerged much later.
Step-by-step explanation:
The Egyptians and Greeks used strong smells to treat mental illness because they believed that mental illness was caused by miasma, a toxic vapor emanating from rotting organic matter. This idea, widely accepted from ancient times until the late 19th century, suggested that bad air or miasmatic odors were responsible for various diseases, including mental illnesses. Treatments during these times often focused on hygiene practices, use of fragrances, and other means to counteract or mask these odors.
Moreover, religious, astrological, and supernatural factors also played a role in the ancient explanations and treatments of diseases. Practices such as incantations and sacrifices were thought to have the power to expiate and cure diseases by pleasing the gods or manipulating supernatural forces. Biochemical theories of brain diseases and the understanding of neurotransmitters came much later, providing more scientifically grounded explanations for mental health disorders.