There have been a large number of studies trying to look at the factors responsible for progressive myopia. There are genetic and environmental factors. Certain races appear to be genetically predisposed to myopia in certain environments eg Chinese and Indian. The evidence seems to point to more time outdoors being more effective.
At present, medication (low dose atropine drops) and special types of contact lenses (orthokeratography or progressive contact lenses) are able to reduce the progression of myopia.