Technology addictions obey the same principles as substance addictions; that is to say, the addiction involves uncompleted impulses and fractured imprinting typically derived from childhood experience (this is not universally the case, but is almost universally the case). The nature of the addiction involves the way in which the addiction completes, temporarily, the unfinished imprinting. The more childhood difficulty an individual experiences, the more likely the individual is to seek multiple substances in adolescence.
Accordingly, the more childhood difficulty an individual experiences, the more likely the individual is to seek multiple technologies in adolescence.
In a Nutshell:
Adolescence begins with the brain pruning stage at roughly age eleven and continues until the end of the twenties (for the youth of today). This long period of development involves the integration of previous developmental stages. Incomplete or fragmented childhood imprinting re-emerges as adolescent psychological difficulty. Addiction is one method of easing the stress of such unfinished imprinting -- by completing it temporarily.
Integration, emotional containment, and identity formation are the central psychological and psychomotoric tasks of adolescence.
These skills are compromised in those who have experience of childhood abuse and neglect, who have difficulty finding healthy groups and peers, who encounter health challenges (such as smoking nicotine or marijuana), and who are otherwise compromised by parenting and/or environment.
Technology addictions (like other addictions) promise but do not deliver integration, containment, and identity formation (IronMan).
A great deal of addictions research supports the notion that adolescents, in particular, are vulnerable to the types of addictions offered by the cultures of technology. The link between video games, emotional desensitization and aggression has been particularly well explored. (Of course, there are some people who insist that violent video games do not promote aggression. These tend to be the same people who insist that smoking cannabis is a health-promoting activity.)
Technology addictions affect health in various ways. A reasonable amount of recreational screen time is healthy as opposed to harmful (about 30 minutes per day seems optimal for adults, about 20 minutes for adolescents, and about 5-10 minutes for children.) Increasing amounts of screen time affect the nervous system (the brain and the body) with increasing severity.