Actually, a lot of research suggests that it is pretty similar to the opioid crisis https://scholar.google.ca/scholar?q=social+media+addiction+s...

If you look at the FB phone app after not using it for a week or so, you will have 1-2 notifications. A few hours after opening the app, 7-10 notifications will appear, creating a false sense of urgency to check the app so you don't miss something. Heroin dealers do the same thing when they notice customers not coming around anymore.

The psychological tactics facebook and others use trigger the release of dopamine just like cocaine, heroin, amphetamines, and gambling.

Can they leave without withdrawals?

Online Social Networking and Mental Health

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4183915/

"Addiction to online social networking, as well as Internet addiction in general, are recent and insufficiently investigated phenomena, frequently discussed and sometimes disputed in the psychiatric literature.30–35 The addictive nature of SNS is supported primarily by the mental preoccupation of many chronic SNS users who as a result tend to neglect other aspects of their social functioning such as family and offline friends. In addition, according to our own observations, sudden cessation of online social networking (i.e., lack of Internet connection) may in some chronic users cause signs and symptoms that at least partially resemble the ones seen during drug/alcohol/nicotine abstinence syndrome."

And just googling "facebook addiction nih", it looks like there is plenty more material of this sort.

It's more complicated than that. People can't defend themselves against that kind of manipulation. It's extremely difficult to leave that site, because they have you put all of your social connections/interactions into the site with no way to export them.