Nicotine is the addictive chemical in tobacco smoke and e-cigarette vapors. And doctors say a teen’s brain is no place for it to end up. Nicotine can reach the brain within seven seconds of smoking a cigar, cigarette or electronic cigarette.

The area of the brain responsible for emotions and controlling our wild impulses is known as the prefrontal cortex (前额叶皮层). It’s very easily affected by nicotine, research shows. This is especially true for young people, because this part of the brain doesn’t finish developing until about age 25.

Nicotine acts like a key to unlocking special receptor (感受器) molecules on the outside of cells in the brain, including those in the prefrontal cortex. Nicotine causes these cells to release signaling molecules, such as dopamine (多巴胺). These chemical signals travel across a gap between nerve cells. When they reach the neighboring nerve cell, they release their message. And it makes users get a feel-good high.

But after repeated exposure to nicotine, those brain cells can change. The effect of these changes is to reduce the body’s ability to release its own, natural pleasure-giving chemicals.

Some of the negative effects of nicotine on the young brain will fade with time — if exposure ends. Others, however, may persist. For instance, brain scientists at VU University Amsterdam found that exposing adolescent rats to nicotine increased their aggressive behavior. It made them a bit more reckless than usual. It also made it harder for them to focus their attention—even later, as adults

No one is sure that the same thing happens in humans, but that’s exactly what worries Garry Sigman. “Exposing the developing adolescent brain to nicotine could lead to a high risk of lifelong addiction,” he explains.

Social media companies are often compared to tobacco companies, for they both market harmful products to children and design their products for maximum customer loyalty (that is, addiction), but there’s a big difference: Teens can and do choose, in large numbers, not to smoke. Social media, in contrast, applies a lot more pressure on non-users, at a much younger age and in a more unnoticed way.

Once a few students in any middle school open accounts at age 11 or 12, the pressure on everyone else to join becomes intense. Even a girl who consciously knows that Instagram can foster beauty obsession, anxiety, and eating disorders might sooner take those risks than accept the seeming certainty of being out of the picture and excluded. In this way, social media unlocks a remarkable achievement: It even harms adolescents who do not use it.

A recent study in the University of Chicago illustrated the effects of the social media trap precisely. The researchers asked more than 1,000 college students how much they would need to be paid to deactivate (停用) their accounts on Instagram for four weeks. On average, the students said they would need to be paid roughly $ 50. Then the experimenters told the students that they were going to get most of their friends to do the same, and then asked, Now how much would you have to be paid to deactivate, if most others did so? The answer, on average, was less than zero — most students were willing to pay to have that happen.

Most students are on social media only because everyone else is too. This is the textbook definition of what social scientists call a collective-action problem. It’s what happens when a group would be better off if everyone in the group took a particular action, but each actor is discouraged from acting, because unless the others do the same, the personal cost outweighs the benefit. Cigarettes trapped individual smokers with a biological addiction. Social media, however, has trapped an entire generation in a collective-action problem.

Prashant Mandal shares a small hut with his wife and four kids, lives on less than $2 a day and recently suffered medical debts of more than $4,000 after his teenage son got sick last year. Yet, despite Mandal’s modest earnings, he spends 20 percent of his income on solar energy, an expense which is key to drawing in customers and helping his children to study. Across the globe, about 1.2 billion people live without electricity. Such limitations are not only inconvenient, but they put people in low-income countries at a greater risk of developing serious health condition. People living without electricity typically rely on kerosene lamps and other harmful light sources, which can lead to burns, injuries, poisoning and other risks .

Realizing the need for a more efficient energy source, a handful of for-profit companies have developed business models that enable under-served people to purchase (购买) solar energy, and, in turn, protect themselves and the environment in the process. Simpa Networks, which focuses its efforts on rural India, is such a company that has found a way to make solar energy affordable and accessible to people in need. Customers are charged a small down payment. Then, through its “progressive purchase” model, they pay in advance for a designated (指定的) amount of energy consumption. A number of other companies have found ways to get solar energy into the hands, and homes, of people who typically can’t afford electricity. MPOWERD, a New York-based company, invented an inflatable solar light that is powered by the sun, and is also able to store that energy.

The Luci, which can provide light for up to about 12 hours, is marketed in the developed world as an efficient camping light. Those sales allow the company to keep its production costs down so that they’re actually affordable in low-income countries. “Energy poverty is discouraging but solvable if we all work together,” said John Salzinger, MPOWERD’s co-founder. “Every single consumer’s purchase helps us reduce costs, and then we pass those savings on to those who need affordable lights the most.”