Methylphenidate is one of the stimulant medications used mainly to treat attention deficit hyperactivity disorder (ADHD) in children. The brand-name versions of the drug include Ritalin and Concerta. All the stimulant medications used to treat ADHD work by augmenting the activity of dopamine in the brain. Dopamine influences many cognitive processes, including executive function.

But when methylphenidate has been tested as a treatment for older people with cognitive deficits, the results have been a mixed bag: some promising, some not so much, which leaves room for more research but hardly a clear path into everyday clinical practice.

Furthermore, the drug’s effect on memory, depression, and various other aspects of mental life has been measured, but very few studies have tackled executive function head on. In 2003, British researchers reported that methylphenidate didn’t seem to have much of an effect on an older brain. The “cognitive effects of methylphenidate are grossly attenuated” in the elderly, they said in a summary of their results (the abstract).

Their study included 60 older male volunteers who were given methylphenidate or a placebo and then took several tests used to assess memory, attention, and executive function. The men taking the drug did no better on those tests than the men taking the placebo. However, they were healthy, so this trial wasn’t intended to be a test of whether methylphenidate might help those cognitive deficits.

As a practical matter, methylphenidate has been used to treat depressive symptoms, fatigue, and apathy in older people with an advanced disease of some kind and those receiving palliative care, which is care designed to provide comfort and pain relief, not treatment of the underlying condition.

Dr. Susan Hardy, a University of Pittsburgh researcher, identified 19 trials testing methylphenidate for this purpose and published a review in the February 2009 issue of American Journal of Geriatric Pharmacotherapy.

She concluded that the “conflicting results, small sample sizes, and poor methodologic quality” made it difficult to draw any conclusions about whether methylphenidate worked for the depression, fatigue, and apathy experienced by people who are gravely ill. Nevertheless, her take-home message was that it was still “appropriate” to use the drug in the absence of definitive evidence of efficacy but with fair good evidence that it was tolerated well.

Some recent results for methylphenidate have been a little more promising. In 2008, Brazilian researchers reported that 10 mg of the drug improved the persistence of recently acquired memories in healthy volunteers of all ages, including those in an older group (ages 61 to 82).

A group in Japan reported in The American Journal of Geriatric Psychiatry in 2008 that methylphenidate helped people with “vascular depression” — depression after a stroke or MRI-documented vascular problems in the brain — who hadn’t responded to regular antidepressants. This was a small (11 patients) study based on a retrospective review of medical records, not a randomized clinical trial.

An Israeli group reported positive results from a study that was a randomized trial. The study included 26 older people (average age 74) without dementia but with some subjective complaints about having a bad memory. The study volunteers were given a single, 20-mg dose of methylphenidate or a placebo pill and then took a variety of tests. The researchers reported that results from the tests show that the single dose of methylphenidate did seem to improve certain aspects of executive function, mobility, and gait, which they speculated might reduce the risk of falling. The notion is that with age, people need more executive functioning to walk properly, so the risk of falling increases as executive functioning declines. These results were first reported at medical meetings in 2007, but the first full article was published in the April 2008 issue of The Journal of the American Geriatrics Society.