At age 45, people who reported using cannabis weekly or more frequently over the past year showed greater cognitive decline than those who never used cannabis, according to a report published this week in AJP in Advance.
“[C]annabis use is increasing among baby boomers (born 1946–1964), a group who used cannabis at historically high rates as young adults and who now use cannabis at historically high rates as midlife and older adults,” wrote Madeline Meier, Ph.D., of Arizona State University and colleagues.
Meier and colleagues analyzed data from the Dunedin Longitudinal Study, a birth cohort of participants (93% White) born between April 1972 and March 1973 in Dunedin, New Zealand. All participants were assessed regularly starting at age 3 until age 45. Starting at age 18, the participants were interviewed every three to six years about their substance use and past-year substance use dependencies, including their use of cannabis, tobacco, and alcohol. Long-term cannabis users were defined as those who were dependent on cannabis or used cannabis weekly or more frequently in the past year at age 45, and also reported using weekly or more frequently at one or more previous assessments. Long-term tobacco users were defined as those who smoked daily at age 45 and reported smoking daily at one or more previous assessments. Long-term alcohol users were defined as those who drank weekly at age 45 and had a diagnosis of alcohol dependence at two or more assessments.
Cognitive tests were conducted at ages 7, 9, and 11 using the Wechsler Intelligence Scale for Children-Revised and again at age 45 using the Wechsler Adult Intelligence Scale-IV. Additional neuropsychological tests were administered to measure the participants’ verbal learning, attention, memory, processing speed, and more. The participants also nominated people “who knew them well” at age 45 to be informants for the study. Informants completed questionnaires, indicating whether they believed the participants had problems with memory and attention over the past year.
Of 938 participants who were assessed at age 45, 86 were considered long-term cannabis users. Relative to the normative IQ of 100, long-term cannabis users had average IQs as children (99.3) but below-average IQs as adults (93.8). Participants who never used cannabis had an increase in IQ of 0.7 points between childhood and adulthood. Long-term users, however, had a mean childhood-to-adulthood IQ decline of 5.5 points, which was significantly larger than the IQ decline of 1.5 points and 0.5 points among, respectively, long-term tobacco users and long-term alcohol users. Long-term cannabis users were described as having more memory and attention problems by informants than less persistent users. Further, long-term cannabis users had poorer learning, memory, and processing speed than long-term tobacco or alcohol users.
“[R]esearch is needed to ascertain whether long-term cannabis users show elevated rates of dementia in later life,” the authors concluded. “This is important given the huge burden of dementia, and it is timely given the confluence of two trends: the growth of the aging population and the record high rates of cannabis use among today’s older adults.”
For related information, see the Psychiatric News article “Cannabis Withdrawal Syndrome Affects Nearly Half of Those Who Quit.”
(Image: iStock/Yarygin)
Registration for MindGames Closes March 16
MindGames, APA’s national residency team competition, is a fun way for residents to test their knowledge on patient care, medical knowledge, and psychiatric history while earning bragging rights for their program. Teams are composed of three residents and must complete the qualifying exam in one, 60-minute setting. Only one team per institution may compete. 2022 MindGames will be held virtually during APA’s Annual Meeting Online Experience. Registration closes Wednesday, March 16, at 11:59 p.m. ET.