Children in grades 3 to 5 who own cell phones are particularly vulnerable to cyberbullying, a new study shows.

In August, a judge warned the nation would have "blood on its hands" if the NHS continued to delay finding an inpatient bed for a 17-year-old girl who had tried to kill herself several times. After his intervention, a bed was found.Just last week, the NHS watchdog released a report warning that children with mental health problems are waiting up to 18 months for treatment. "We should put our efforts into getting more resources, because if we put them into increasing awareness we just increase wait times and burn out our staff," says Wessely.

Further, even a rise in self-harming may not indicate a rise in distress. "There seems to be more self-harm happening, but it's not completely clear this is due to a greater level of underlying distress," says Max Davie, a paediatrician in London who treats children with this behaviour. "It may be becoming a more culturally acceptable way to show your distress."

So are these new skills a good or a bad thing? Neither, she says. "It's just a way we have of adapting to our environment."

But some scientists contend that there isn't enough evidence to condemn smartphones. "I see the rise in depression, especially among girls, and I understand why people are making these connections with new technologies," says Candice Odgers, a professor of psychology and neuroscience at Duke University who has published research on teenagers and tech. "But so far we have very little data to suggest mobile technologies are causing anxiety or social impairments." She points to evidence that some young people, particularly marginalized groups like LGBT youth, can derive benefits from online support networks and communication with friends and family. Odgers adds that jumping to conclusions and vilifying smartphones may lead us away from factors that may turn out to be more significant—a worry raised by other experts.

"What we're seeing in our work is that young people are constantly distracted and also less sensitive to the emotions of others."

To understand how device use may be affecting a young person's mental health, it's important to recognize the complex changes occurring in an adolescent's still-developing brain. For one thing, that brain is incredibly plastic and able to adapt—that is, physically change—in response to novel activities or environmental cues, says Jensen, who is also the author of The Teenage Brain.

“Today’s teenagers have less freedom to wander than any previous generation.”

“I often heard parents complain that their children preferred computers to ‘real people,’ ” Boyd writes. In her research, however, she discovered that they would much rather hang out with their friends in person. But they can’t.

"PauseApp employs research about the link between time spent on social media and feelings of loneliness, anxiety and depression," Floyd said. "With PauseApp, you see in real time whether you are overdoing it and possibly setting yourself up for these mental health dangers."

After all, rationally considered, how can you love and hate somebody at the same time?

Being glum can be advantageous and has been shown to sharpen our eye for detail, for instance. But, overall, the brain seems geared towards maintaining a mildly positive frame of mind. Being in a good mood makes us more likely to seek new experiences, be creative, plan ahead, procreate and adapt to changing conditions.

Many regions fundamental to mood are buried deep in the most primordial parts of the brain; that is, they are thought to have been among the first to develop in the human species. This is probably because mood is evolutionarily important.

The brain regions on their list process conflict, pain, social isolation, memory, reward, attention, body sensations, decision making and emotional displays, all of which can contribute to feeling sad. Sadness triggers also vary—for example, the memory of a personal loss; a friend stressing over a work conflict; seeing a desolate film.

In 22 studies, brain scans were performed on nondepressed but sad volunteers. Sadness was mostly induced (subjects were shown sad pictures or films, asked to remember a sad event), although, in a couple of studies, subjects had recently experienced a loss. In the aggregate, sadness appeared to cause altered activity in more than 70 different brain regions.

After getting a glimpse of joy, why do some people immediately shift back to what doesn't work?

For some, happiness is fleeting and depends on their present circumstances, whereas others seem to be generally happy or generally unhappy no matter what is happening in their lives.

A basic assumption of human behavior is that people pursue pleasure and seek to avoid pain. Then why is it that some people seem content to wallow in their misery, even boasting about it as some sort of badge of honor?