So if the a significant other won't "allow" your kid to socialize with friends and is continually checking your child's Facebook status updates to see who they're hanging out with, "all of those things take away from that young person's sense of self," Lancaster said. "It becomes much more of this person is trying to take over their lives."
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What do you do in this scenario?
"You should be able to honestly say, ‘I don't like this person, you're not yourself when you're with them,'" Lancaster said.
What to do when they break up
"Teenagers notoriously have this black and white thinking," Lancaster said. "‘This is The One, he'll only be The One' or ‘I'll never be able to survive without her.' ‘She was the best thing that ever happened to me.'"
But then next week, the Next Best Thing That Ever Happened to them comes along.
Lancaster suggests parents say something like, "I can tell you have strong feelings for this person, and I hope it works out for you, but just in case, what will happen if you find someone else that you like better? What will happen if they find someone else that they like better? What will happen if your boyfriend or girlfriend does something that's totally inappropriate?"
Exclusive dating and sexual activity complicate teen breakups, Lancaster said.
If after the breakup your child is showing symptoms that don't seem to resolve themselves after two weeks — symptoms like losing weight, feelings of being so distraught or so upset that they've mentioned suicide or harming someone else — it might be depression.
"That's the time to get a mental health intervention, go to the emergency room," Lancaster said.
Puppy love? Love sickness? No such thing.
"Those terms have been around since I've been a kid," Lancaster said. "No, it is not a diagnosis. But I think that whole concept — this idea of being in love with the feeling of being in love, has been around for a very long time."
We all like that heightened sense of excitement, the boost of feel-good endorphins that makes us feel better when we're in love.
"That's why love is such a powerful emotion," Lancaster said.
But being in love turns into something dysfunctional when it causes people to change — sleep deprivation because of nonstop texting or an obsession with who the significant other is talking to.
Eventually, there should comes a point when the teen realizes that while he or she might think this person might be The One, they realize that the person isn't their entire world, Lancaster said.
"I still have to go to school every day, I still have to do things with my parents every day. I still have to go to the orthodontist — all of those things that are part of my life," she said.
"When people feel like they can have a life apart from that person, I think that's one of the hallmarks of maturity," Lancaster said.