People in their 20s and 30s are spending hundreds of dollars to treat or prevent "tech neck." Marina Demeshko/Getty Images Nora Ephron was around 62 when, in 2003, she wrote that she felt bad about her aging neck. Today, a distinctly modern phenomenon known as "tech neck" is leaving people as young as their early 20s feeling the same way. Though not an official diagnosis, the term " tech neck " is popular on social media and recognized by dermatologists, plastic surgeons, and physical therapists. It refers to horizontal lines or creases on the neck, as well as postural changes such as rounded shoulders and a forward head position. Anyone can get tech neck, but based on social media posts, women in their 20s and 30s are most concerned about preventing or "fixing" its signs, with some spending upward of $5,000 to reduce fine lines and improve posture . Lindsey Wallace, a 35-year-old marketing director based in Los Angeles, first learned about tech neck from an Instagram reel.…