We have been experiencing a large increase in the numbers of recognised cases of developmental difficulties for decades now. When many were only identified in the late 70's and 80's this is understandable, but this shouldn't account for the numbers we see today. There are many possible reasons;

Dietary Changes
Differences in pregnancy routines and standard practice
Changes in the birthing process
Other environmental changes (pollution/stimulants/medicine)

The issues caused by excess screen time namely; blue wave light stimulation, changes to the bodies circadian rhythm, overstimulation to hormonal imbalance amongst others, are well documented. See article below.

https://www.psychologytoday.com/blog/mental-wealth/201508/screentime-is-making-kids-moody-crazy-and-lazy?

But one other change to consider, is the lack of movement children are making. When continuously glued to iPads and tablets, they are becoming far more sedentary then ever before. Granted there have been books in the past that caused some children to be more sedentary and less active then others. However with iPads being so addictive and the many varying tasks (games, reading, internet, videos) that children can do on them, instead of just getting bored of reading, children will be seated with one all day, given the opportunity.

This lack of movement is halting vital developmental processes. Children engage certain movements when younger to stimulate developmental reflexes and progress onto adult postural reflexes. Most infant and primitive reflexes should be gone by the time the child can walk, but they can be retained longer. If there is such little movement after this stage, the cases where reflexes have retained longer then their natural timeframe, will be far less likely to release on their own accord. Perhaps this is leading to the rise in the number of cases we see today? See article below for other issues arising from lack of movement in youth.

https://www.psychologytoday.com/blog/freedom-learn/201001/the-decline-play-and-rise-in-childrens-mental-disorders?

How can we alter this?

The truth is the change needs to start closer to home then we think. On occasion I have parents in the clinic glued to their phone throughout the sessions. If this is the image a child see's, they are only going to want to emulate this themselves.

We could all do with less screen time, myself included.

Put down the phones/tablets and turn off the TV. Encourage face to face interaction, playing outside and creative games that utilise a childs' fantastic imagination.

While possibly met with resistance to begin with, not to mention harder to regulate/encourage/participate in as a parent, over time the rewards will be noticed by all. In development, confidence, social skills and most importantly, happiness.