Mescaline hydrochloride is primarily used in research settings to study its psychoactive effects on the human brain. It is often employed in neuroscience and psychology experiments to understand altered states of consciousness, perception, and cognition. Additionally, it has been utilized in ethnobotanical studies to explore its historical and cultural significance in indigenous rituals and spiritual practices. In clinical research, it is sometimes investigated for its potential therapeutic effects in treating mental health conditions, such as depression and PTSD, though this remains experimental and not widely accepted.