The reddit dancer sex videointernet can lift you up as quickly as it tears you down.

At least that's how it seems to some teens and young adults who build rewarding relationships on social media but also, at times, feel rejected or excluded by friends and strangers.

This complicated grey area -- where social media both connects and isolates us -- is rarely captured in the way we talk about how young people live online. Platforms like Facebook, Snapchat and Instagram either bring people together in novel and fun ways, or they breed narcissism and become a hunting ground for cliques and bullies to prey on vulnerable kids.

What these alternately sunny or apocalyptic portrayals often miss is exactly how social media use influences the way young people see themselves. The concern isn't just that social media, for better or worse, has transformed the way we communicate -- it's that those tools may radically affect how adolescents and teens forge their own identities at critical moments in their lives.

Naturally, scientists have a lot to say about this phenomenon. First, you can safely assume, without being an alarmist or buzzkill, that it's a legitimate concern. Two recent studies both showed that social media use can be associated with feeling lonely and low.

The first, published Monday in the American Journal of Preventive Medicine, showed that the more young adults used social media, the more they felt isolated. A systematic review published online last week in Adolescent Research Review, found a small but statistically significant correlation between social media use and depressive symptoms in adolescents and teens.

The question that neither study can conclusively answer is why social media use might lead to these experiences, but the researchers behind them have some ideas.

Dr. Elizabeth Miller, co-author of the American Journal of Preventive Medicine study and professor of pediatrics at the University of Pittsburgh School of Medicine, says that young people both find solace and angst in social media.

Miller says that kids who feel marginalized because of a disability or because they identify as lesbian, gay, bisexual, transgender or queer, for example, may encounter bullying, but they can also construct supportive communities defined by affirmation and belonging.

In the same breath, however, Miller can also talk about girls who feel smothered by the expectation to be online constantly. One research participant once told her that social media can make it feel like you're being watched 24/7.

"You can't post anything, because you can't trust anyone," Miller says, summing up the constant fear of posting the wrong thing and then paying a social price for it. In some ways, that fear is age-old; just ask anyone who has ever cracked a joke at the cafeteria lunch table and heard nothing but crickets. Still, before the rise of social media, the embarrassment of those moments often evaporated by the end of the day, whereas now they can be archived and resurrected through a simple screenshot.

Miller and her co-authors speculate that people might feel increasingly lonely the more they use social media for a number of reasons. They might substitute online activity for face-to-face interactions. They might see highly curated and unrealistic portrayals of other people's lives and feel like they don't measure up. It may also be that people who already feel alone and isolated seek relief in social media, hoping to make connections that are elusive in real life.

Miller's study, which surveyed people on their social media use and measured their perceived isolation, wasn't designed to determine whether social media is directly responsible for feeling isolated or lonely. She and her co-authors emphasize the need for further research to resolve that question, but argue the stakes are pretty clear.

Typical adolescent and young adult development involves a fair amount of self-obsession. As teens try out their identities, social media becomes a natural venue for that performance, but without the same requirements or expectations for interpersonal communication that young people had to navigate just a few decades ago. Having a difficult conversation in person, for example, about your values or beliefs can mark a developmental milestone and is a useful life skill. Being able to judge a person's non-verbal cues during an exchange is essential for socializing. Miller worries that not every young person is getting those experiences now.

"Part of being human is, of course, our ability to communicate verbally and we have to figure out opportunities for young people to do so in safe environments where they don’t feel like they’re going to be judged," says Miller.

Moreover, if social media somehow creates or worsens feelings of loneliness or depression, it may lead to serious mental health problems, including suicidal ideation or behavior.

Young people with fragile self-esteem may be particularly vulnerable to the negative effects of social media use, says Sheryl Gettings, co-author of the Adolescent Research Review study and a tutor in the Department of Child and Family Health at King's College London. Gender also seemed to play a role in people's experiences with social media, according to the studies Gettings and her co-authors reviewed.

Several noted that girls and boys used the internet for different reasons, and that by investing more in social media, girls enjoyed the benefits but were also more prone to feeling bad about themselves as a result. This dynamic, the authors suggested, could be rooted partly in experiences of physical objectification (i.e., selfies can be a source of affirmation and torment).

The point of this research, says Gettings, isn't to condemn social media or descend into moral panic about the impact of technology on our kids' minds. Instead, it's to take seriously the idea that some adolescents and teens may face different challenges on social media and need caring adults and peers to help them negotiate the rough passages. The danger, she says, is oversimplifying good and bad experiences.

While the emotional turmoil of growing up will never go away, whether in real life or on social media, the least we can do is acknowledge that it's more complicated than ever.