Here is a report on an article I haven't read, which shows that the more frequently a college freshman texts, the worse their sleep patterns are. They mention that one cause underlying that is the pressure they feel to respond to texts no matter when, and that their text-messenger ("phone") may be lying next to them at night, interrupting their sleep.
This is a clear symptom of OCD -- the strongly felt need to obsessively check and re-check the status of something, and to deal with it time and again through compulsive behaviors. In particular, for no real goal to have been accomplished at the end of all the checking and compulsive responding. Indeed, worse than just wasting time, their obsessive-compulsive behavior may be harming their basic, daily well-being -- like keeping them from getting a good night's sleep.
It might seem strange to suggest that an entire generation has OCD, but if that sounds odd, you haven't been around many Millennials.
Frequent texting also predicted greater vulnerability to stressful times in a social relationship. If you were already heading in the stressed-out direction, being an excessive texter made it worse. It's suggested that texting in a troubled time makes things worse because the lack of nuance and non-verbal communication allows a volatile situation to explode or melt down.
The study author was born in the late '60s and must have spent lots of time talking on the phone as a teenager during the '80s. So she knows that the face-to-face qualities aren't that important for effective communication. In general, the non-verbal only enhances the verbal, and is redundant. It makes for more vivid and memorable conversations, but isn't necessary. The only time when the verbal and non-verbal give opposite signals is when the person is lying. But in general, someone you're spending that much time on the phone with won't be lying to you.
Rather, the defect seems to be in literate as opposed to oral communication. When we digitize speech into literate chunks, we lose all the analog stuff -- inflection, pacing, stress, and so on. Not to mention non-linguistic sounds like laughing -- and what kind of laughter. That's hard to send in literate form.
There's also the analog changes in the person's face and mouth when they feel different emotions while talking. You can hear it when someone is smiling because the lips aren't in their usual position, their corners pulled up and back, pressing the top and bottom "rows" of the lips closer against the teeth. It just sounds different, and you know from experience that this deviation is caused by the lips deviating in a manner consistent with smiling. Lips tensed in anger make for another unusual shape to the vocal tract, and you can hear that too.
Whatever the link between excessive texting and fragile social relationships turns out to be, they are probably both co-symptoms of OCD and the related avoidant attachment style. Keep everything and everyone away because it could contaminate you or somehow else just get awkward. Dealing with others is awkward, so we won't deal with anyone. How will we still communicate with others, though? Just send a shitload of texts instead of calling them on the phone.
Technology does not force its adopters to use it in any particular way, but the other way around. If people hadn't gotten so avoidant and retarded over the past 20 years, perhaps cell phones would never have developed the texting feature. Normal people only used landline phones to talk, and that was quite stable from the 1960s through the early '90s. Only during the mid-'90s when America Online offered a primitive form of text messaging (Instant Messenger) did people begin to send literate messages to one another from the privacy of their own home, rather than call the person up.
(Even there, at first you only IM'ed people who were far away and would've costed a lot to call up, or who you'd never met in real life. IM'ing started out like a chatroom, only with two people. By the late '90s, it had become more common to IM your real-life friends instead of calling them up or hanging out with them.)
The fact that cell phones not only developed the texting feature, but that this would become the predominant way that the adopters would use it to communicate, just goes to show how socially-emotionally avoidant young people had become.
One last important thing: remember that "excessive" texting here is defined relative to the behavior of other college freshmen. I'm surprised they found a strong relationship between texting and anything because you'd think that all kids these days are hardcore texters, so you couldn't set aside the high-frequency from the low-frequency texters. (That would be a "restriction of range" problem.)
To really throw light on how texting frequency relates to sleep patterns, mental health, and so on, they'd need to look at young people who don't text much at all. See the characters in any classic teen movie from the '80s -- whatever their troubles may have been, they had a basic resiliency and didn't melt down or retreat into a cocoon, hoping their problems will magically go away.