You should be concerned. LSD is one of the most intensely psychoactive drugs ever invented. It binds to the GPC receptors in the brain and it's effects are wide ranging. Even small amounts can be destructive or even lethal. Moreover, the effects/dangers are usually cumulative.
If your friends think it can't hurt them, they are in for a severe ( or deadly ) shock. The physical effects aren't as bad as the psychological but they can include rapid heat rate, unsafe blood pressure increase, muscle cramps and gradual muscle deterioration, gradual breaking down of tendons, severe insomnia and tremors.
As for the mental effects, they are legion. LSD can cause
permanent personality shifts. It can diminish cognitive abilities and overall perception. It can damage the nervous system. It efects vary greatly from person to person but they are always negative.
Lastly, I'll give you a real life case. Several years ago, I knew a girl who was a former LSD user. She was only twenty and had been off LSD for over two years. Nonetheless, it had caused irreparable damage. She couldn't look at a pattern ( like a dish towel or wall paper ) without feeling a sense of sheer terror. She had almost no sex drive. She could barely feel pain which led her to a severe burn because she didn't realize it was happening.
Ask your buddies if this sounds like fun?
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