Moderate drinking isn't as safe as some previous studies have suggested. And habitual heavy pot smokers often find themselves in a serious downward spiral by the time they reach their late 30s.
Those are the buzz-killing findings of two separate studies released on Tuesday. One offers evidence that long-time, consistent cannabis use is associated with "more financial difficulties, workplace problems, and relationship conflict by early midlife."
The other reports that the widely held belief that moderate drinkers live longer than teetotalers is, in fact, the product of flawed research.
It's all enough to prompt you to reach for.... Hey! What's left?
The marijuana smoking study, published in the journal Clinical Psychological Science, used data from the Dunedin Longitudinal Study, which followed about 1,000 New Zealanders from birth to the age of 38. Two separate issues—persistent, regular cannabis use, and dependence upon the drug—were assessed at ages 18, 21, 26, 32, and 38.
So much for pot making you mellow.
"Persistent" users were those who reported at three or more of the five assessments that they smoked pot four or more days per week. Dependence was diagnosed using criteria from the Diagnostic and Statistical Manual of Mental Disorders.
The research team, led by Magdalena Cerdá of the University of California–Davis, found "many persistent cannabis users experience downward socioeconomic mobility, and a wide range of associated problems."
Specifically, those with "a longer history of cannabis dependence, or of regular cannabis use, were more likely to experience financial difficulties, including having trouble with debt and cash flow (such as defaulting on a credit card payment or missing a loan payment); difficulty paying basic expenses, such as food and rent; food insecurity; being on welfare; and having a lower consumer credit rating."
Persistent heavy pot smoking, whether or not it reached the level of dependence, "was also associated with anti-social behavior in the workplace, and higher rates of intimate relationship conflict, including physical violence."
So much for pot making you mellow.
Importantly, these associations were still found after the researchers took into account a variety of factors, including family history of drug or alcohol abuse, and socioeconomic adversity in childhood. "The more years of cannabis dependence, or regular cannabis use," they write, "the worse the societal and economic problems."
The findings present a cautionary tale to states considering the legalization of marijuana for recreational use. "Heavy cannabis use and dependence," the researchers conclude, "was not associated with fewer economic and social problems than was alcohol dependence."
Speaking of alcohol, another newly published study throws into serious question past research that found moderate drinkers have a reduced mortality risk. A research team led by psychologist Tim Stockwell of the University of Victoria reviewed 87 studies that examined that question, and found most of them were deeply flawed.
The issue, they write in the Journal of Studies on Alcohol and Drugs, is that most such studies compared the longevity of moderate drinkers with that of abstainers—a group that included ex-drinkers. Many of these teetotalers "gave up drinking for health reasons," they write—a fact that skews the numbers, since the life expectancy rates of such people are relatively low.
The researchers report that only 13 of the 87 studies they examined avoided this bias, and they found drinking did not convey any significant health benefits.
After re-examining the evidence, Stockwell and his colleagues conclude that "low-volume alcohol consumption (that is, having two drinks per day) has no net mortality benefit compared with lifetime abstention or occasional drinking (defined as less than one drink per week)."
The results echo those of another study published last year that also strongly questioned the benefits of moderate drinking. The assertion that alcohol, in moderation, is good for us, and the belief that heavy, long-term marijuana smoking is harmless, both lie on very, very shaky ground.
Findings is a daily column by Pacific Standard staff writer Tom Jacobs, who scours the psychological-research journals to discover new insights into human behavior, ranging from the origins of our political beliefs to the cultivation of creativity.