It takes someone who has no understanding of how hormones work to make the claim that casual sex doesn't have any long-term repercussions to the individuals involved.
During sex, and especially during orgasm, the hormone oxytocin is released, which prompts emotional bonding. This happens in both sexes, but is especially pronounced in women. There are theories that this was an evolutionary developments in humans that resulted in the creation of the stable family unit, which gave offspring a better chance to survive and thrive.
Casual sex prompts the forming, then breaking, of bonding with partners. Repeated bonding with different partners dulls the individuals' response to the hormone, which leads to difficulty with creating and maintaining a relationship.
It also causes depression and anxiety in young women.
Even if the participant manages to avoid STDs and unplanned pregnancy, casual sex is harmful. Always.
Any claim otherwise is an attack on young people in general, and young women in particular.
Ironic, isn't it, that it's the radical feminists pushing casual sex on young women?
2 hours ago