There is no evidence to support that Invisalign is only for kids.  Although It may be true that the younger you start the teeth straightening process the less time you might have to wear them for, every case is different and that evidence is largely based on how teeth straightening issues can worsen over time.
When asked about orthodontic issues with young children our cosmetic dentist Halim Sbenati stated “Invisalign helps prepare new adult teeth for an eruption to Increase the likelihood of them coming in naturally and straight.  This is a great preventative measure that we knew would greatly benefit our customers by taking early action against; crowding, gaps, over/underbites, and Improving their oral health and self-esteem before It ever becomes a problem.  He hopes others will do the same as well.
A lot of adults suffer from dental complications like tooth decay and periodontal diseases which if left untreated can lead to tooth loss, general health issues, and an overall decrease in quality of life.  Adults who are happy with their smiles have Increased self-esteem improving their comfortability and efficiency, family life, work-life, functional capabilities while smiling more.