Although the name adolescent idiopathic scoliosis (AIS) includes the word adolescent and implies a condition limited to teenagers, the age of onset can be pre-pubertal (before puberty or adolescence). This is especially true among girls who develop AIS. And of all the different kinds of scoliosis (subgroups are based on cause), AIS is more likely to affect girls than boys.
The average age of girls entering the biologic phase of puberty and adolescence may be dropping. There are reports of puberty beginning as early as age seven in some girls. The whole idea of earlier development in females remains under investigation. Results have been mixed and all studies have not reached the same conclusions.
The true cause of AIS remains a mystery. Despite 20 years of intense research and study, the best we can say is that it is a multifactorial condition. In other words, there are probably many causes linked together. Hormonal influences, growth factors, genetics, diet and nutrition, and many others could contribute to whatever mechanism turns on this problem.