I am the adult child of alcoholics and have at least one non recovering alcoholic in my family now.
I had a nephew who literally killed himself with alcohol and hard drugs.
Another nephew has been in and out of prison several times now due to illegal drug use and sales; addicted to drugs and alcohol.
I have had close relatives with gambling addiction to the point it ruined their lives.
I have a friend who is a compulsive orderer and hoarder.
And none of them were any more addicted or damaged as much as a niece who is hopelessly addicted to marijuana. She has multiple health problems including serious scarring of the lungs from years of smoking pot. She cannot go without it without unbearable withdrawal symptoms. She refuses to acknowledge the problem or get help.
Marijuana may not addict as quickly or strongly in most as does heroin or cocaine or other hard drugs, but anybody who says it is not addictive is just in a state of ridiculous denial.
(I am from a very large family and the vast majority of us are just fine.

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