Pica is normally diagnosed as a disorder in childhood however no disorder can be isolated to an age range. The Gale Encyclopedia of Mental Disorders has this to say about Pica:
A few of the posters experiencing symptoms mentioned they are not pregnant now. While pica can begin during pregnancy it also continues to occur intermittently for years after pregnancy.
If its a nutritional deficit, it will resolve when the deficit is treatment. Behavioral modification has been minimally effective.