CHICAGO (CBS) — Two heavyweight Apple shareholders are pressuring the company to do more to protect children from the potentially harmful side effects of excessive technology use.

Furthermore, CBS 2’s Vince Gerasole reports they are urging Apple to research whether cell phone use in teens is a distraction or an addiction.

In an open letter posted online this weekend, the investors — Jana Partners and the California State Teachers’ Retirement System (CalSTRS) — say, “[T]here is a clear need for Apple to offer parents more choices and tools to help them ensure that young consumers are using their products in an optimal manner.

“There is a developing consensus around the world including Silicon Valley that the potential long-term consequences of new technologies need to be factored in at the outset, and no company can outsource that responsibility,” the letter said. “Apple can play a defining role in signaling to the industry that paying special attention to the health and development of the next generation is both good business and the right thing to do.”

Jana and CalSTRS go on to say that Apple needs to take a more active role in researching whether excessive iPhone use, with addictive qualities and exposure to cyber bullying, can be bad for young minds.

“In the last several years, we have seen that there is an increase in teen suicide rates, unfortunately, as well as a lot of mental health problems,” Dr. Sheela Raja said, who is a clinical psychologist. “I would say it’s really picked up in the last 3 or 4 years.”

Dr.  Raja says that rise in teen mental challenges coincides with wider cell phone use. “We don’t really understand what is the effect on kid’s brain development, what is the effect on their socialization?”

Erin Thomason, for example, says she likes to learn about art projects on Instagram. However, she, and other students at St. John of the Cross Parish School, know during the academic day, their phones need to be in their backpacks or lockers and turned off.

“Because if it’s in their hands, they’re going to use it the way they are most familiar with it — through the texting,” said the school’s principal, Kathleen Gorman.

For the moment, teenagers, their schools and families are learning how to cope on their own.

“Sometimes I just won’t charge my phone, because I will keep using it and using it and using it,” Thomason said.

Jana and CalSTRS together control about a $2-billion stake of Apple’s nearly $900-billion market value.

Apple has yet to respond to the letter.