The actress Tatum O’Neal was arrested recently on charges of buying crack cocaine from a man on the street near her New York City home. She is a 44-year-old mother of three. She has spent years in and out of drug abuse treatment (which she chronicled in her 2004 memoir), and according to her publicist she will continue to “attend meetings” for drug and alcohol abuse.

Ms. O’Neal illustrates a disturbing trend among those being admitted to substance abuse treatment services: a growing percentage of older women are being treated for harder drugs.

Data from the Substance Abuse and Mental Health Services Administration revealed that the total number of admissions to treatment services from 1996 to 2005 (the last year for which detailed data are available) stayed about the same among people under 40, but jumped 52 percent among those 40 and older. Of the 40 and older group, the rise in admissions among men was 44 percent. Among women, it was 82 percent.

(During the same span, the population in the United States age 40 and older grew by only 19 percent.)