The pharmacological action of methamphetamine is quite well understood.
How Methamphetamine Can Cause a Sudden Stroke
Astrokeis because of diminished blood supply to the brain.
Over time, psychosis may develop and persist even after the drug is no longer present in the body.

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The substance is extremely addictive for a number of reasons.
The user typically wishes to repetitively experience the sense of euphoria produced by methamphetamine.
These physical factors feed the addictive quality of methamphetamine.
The risks of methamphetamine are life-threatening, as the drug may cause death or severe disability.
National Institute on Drug Abuse.What are the immediate (short term) effects of methamphetamine misuse?
2019;39(9):1739-1746. doi:10.1161/ATVBAHA.119.312461
Richards JR, Laurin EG.Methamphetamine toxicity.
Treasure Island, FL: StatPearls Publishing.