Well, you know, I’m not exactly an expert on this topic, but I’m going to try my best to provide some sort of reasoning as to why this could be...
1. Sexting releases more hormones, and causes you too not really think about anything else and focus on... well, sexting.
2. If you don’t get an adequate response from your sexting partner(s) it could cause some sort of mental health issues, like depression. This alone would probably decrease your intellectuality, but if got worse you could start not feeding yourself properly, so your body won’t get enough nutrients, and your brain won’t function as good.
(That one might be kind of a long shot, but it’s what I’ve got.)
All in all, I’ve never sexted anyone, but I think it does decrease your intellectuality. I’m not exactly sure if this is what you meant but I hope I was able to help even a little bit.
