SAN FRANCISCO – An absence of guidelines on cannabis in older adults makes it difficult for clinicians to advise seniors, particularly those who use it for medical reasons, Adrienne Withall, PhD, said at the 2016 congress of the International Psychogeriatric Association.
“We don’t really know the impacts of cannabis use on older people. They may be positive or negative, depending on what it’s being used for,” said Dr. Withall of the University of New South Wales in Sydney.
Dr. Adrienne Withall
Questions about how cannabis affects older people are growing as the boomer generation ages and cannabis becomes easier to legally obtain.
“Our picture of the cannabis user as a young adult or teen is inaccurate,” Dr. Withall said. “Many reports show that adults aged 50 and up are using cannabis for pain management or other therapeutic reasons, although we suspect they are also using it for recreation.” In the United States, regular use of cannabis rose by 455% among 55- to 64-year-olds between 2002 and 2014, according to data from the U.S. National Survey on Drug Use and Health. In Australia, studies of middle-aged and older chronic pain patients, including those without cancer, suggest that about 15% have used cannabis for pain, Dr. Withall said.
Older patients may ask if cannabis causes cognitive deficits. “Anecdotally, the answer is yes. There is certainly evidence in younger cohorts that cannabis affects cognition, although this remains fiercely debated,” Dr. Withall said. She cited a 25-year longitudinal cohort study of persistent cannabis users in which habitual cannabis use during adolescence led to significant cognitive impairment in executive function, information processing speed, and other cognitive domains in adulthood. Importantly, those deficits did not fully reverse after users stopped. In contrast, users who started as adults developed milder cognitive deficits and greater restoration of cognitive function after cessation. In another study that is currently under review, 42% of cannabis-using older adults had significant cognitive impairment (scores of less than 88 on the ACE-R [Addenbrooke’s Cognitive Examination-Revised]), Dr. Withall said.
These users did have comorbid substance abuse, depression, and other potential confounders, but nonetheless, more frequent cannabis use approached statistical significance as a negative predictor of ACE-R scores, she added.
The effects of various cannabis products depend on their ratio of cannabidiol (CBD) and tetrahydrocannabinol (THC), Dr. Withall emphasized. “There is increasing preclinical evidence that the endocannabinoid system regulates neurodegenerative processes common to various dementias, including excess glutamate, glial activation, oxidative stress, and neuroinflammation,” she said. Some studies suggest a neuroprotective role for CBD, while in safety studies, THC was well tolerated in patients with dementia but did not improve cognition. In another 4-week, uncontrolled, open-label trial of 10 patients with Alzheimer’s disease, adding medical cannabis oil to regular care was associated with significant decreases in delusions, agitation or aggression, irritability, apathy, sleep, and caregiver distress, Dr. Withall said (J Alzheimers Dis. 2016;51[1]15-9).
So what to tell patients who ask about cannabis or are habitual users?
“At the moment, we are trying to encourage people to minimize use of cannabis, but we don’t have enough information,” she concluded. “Even though we suspect it is having a detrimental effect on patients, it may be that certain groups are showing benefits. There is just not enough to hang a hat on yet.”
Dr. Withall disclosed no funding sources or conflicts of interest.