“In retirement there can be depression, divorce, death of a spouse, moving from a big residence into a small residence,” said Steven Wollman, a substance abuse counselor in New York, . “For anyone who’s an addict, boredom’s the No. 1 trigger.”

Sandra D., 58, who works in the financial services industry in Toronto, said that her father’s drinking increased so much after he retired that she often took the car keys away from him.

“He and his friends meet for cocktails at about 3 or 4 and then he passes out, which he calls a ‘nap,’ ” said Ms. D., who asked that her full last name not be used. “My dad didn’t plan out his retirement well. My mom was very ill for many years before she passed away, and my dad was a caregiver. He was pretty well looking after the house and taking care of her. When she passed away, there was a very big void for him.”

Ms. D. said her father, an 82-year-old former maintenance worker, doesn’t believe he drinks too much, a common perception among many seniors.

“People are really good at redefining things,” said Stephan Arndt, a professor of psychiatry at the University of Iowa and director of the Iowa Consortium for Substance Abuse Research and Evaluation. “They say, ‘I don’t have a problem, I just like to drink.’ Or, ‘I’m a big guy, I can handle it.’ In the case of prescription drugs, it’s, ‘Well, I got it from my doctor, and it’s for my pain. It’s medication.’ Consequently, they don’t seek help.”

Physicians often aren’t trained to talk to their older patients about chemical dependency — or, perhaps more pointedly in an era of managed care, they often don’t have the time to thoroughly screen a patient. Also, many signs of chemical dependence like memory loss and disorientation resemble normal symptoms of aging. “Is this person confused because they’re messing up their meds, or is it dementia?” said Brenda J. Iliff, the executive director of Hazelden, a residential treatment center in Naples, Fla., that offers special programming for baby boomers and older adults for about $21,000 a month. “Is their diabetes out of control, or did they fall and break their hip because they were woozy from Ativan?”

Another misconception is that older adults don’t benefit from treatment. “There’s this lore, this belief, that as people get older they become less treatable,” said Paul Sacco, an assistant professor of social work at the University of Maryland in Baltimore, who researches aging and addiction. “But there’s a large body of literature saying that the outcomes are as good with older adults. They’re not hopeless. This may be just the time to get them treatment.”