Reading Comprehension — quick quiz

Read the passage and answer the question that follows: The smartphone has revolutionized communication in the 21st century. What once required letters that took days to deliver can now be accomplished in seconds through instant messaging. However, experts warn that excessive smartphone use may lead to social isolation. People are increasingly interacting with screens rather than engaging in face-to-face conversations. Studies show that teenagers who spend more than three hours daily on smartphones report higher levels of loneliness compared to those with limited usage. Question: According to the passage, what is a negative effect of excessive smartphone use?