I believe the cartoons that are created today are geared more toward adults than children. Therefore any one especially adults can watch anime cartoons. You may not want to spin your entire time watching cartoons because that may be a problem. Most people do not spend hours upon hours on watching cartoons or even television. If they do they need to spend more time getting fresh air outside and exercising.
Children like to watch cartoons and at first they were first created for children. Over time people started creating comic books for people of all ages. I think the same can be said for anime cartoons. There may be a time when anime cartoons resort back to children and not adults and at this time you may be too old to watch them.