The World Health Organization(WHO) is about to recognize gaming addiction;asa mental health condition it is called "Gaming Disorder". The WHO defines gaming disorder as a recurring or persistent behavior pattern that is severe enough to affect crucial and important aspects of life. Examples would include gaming taking priority over eating , sleeping or other primary and necessary functions..
For me it's true, the excessive playing of various online games affect to the children's important activities. But your child will not be affected by gaming disorder if you discipline them. Give the time when they can use gadgets and play games.
As a gamer too , this is actually true the meaning of excessive playing is 2hours or more than two hours though , and can affect negatively both health and on the studies though , and mostly the behavior . One of the things that I learn is to have a time management have a self discipline.