Boys who start smoking pot before 15 are much more likely to have a drug problem at 28

What a difference a year or two can make? Well, regarding cannabis-use quite a lot according to to a new study by Université de Montréal researchers: if you started smoking marijuana at the start of your teens, your risk of having a drug abuse problem by age 28 is 68 per cent, but if you started smoking between 15 and 17 your risk drops to 44 per cent.

There is still some caution regarding the study. While they controlled for a lot of different elements, it is still rather a correlation than causal proof. Also the use of a longitudinal sample is great and relevant, but the sample was limited to boys of low socioeconomic status.

From the press release:

“The odds of developing any drug abuse symptoms by age 28 were reduced by 31 per cent for each year of delayed onset of cannabis use in adolescence,” the researchers at UdeM’s Department of Psychology, School of Psychoeducation and the CHU Saint-Justine Hospital Research Centre found.

Their study was publishedApril 22 in the Canadian Journal of Psychiatry.

Percentage nearly tripled

According to a 2011 study by University of Waterloo researchers in the journal Addictive Behaviors, 10 per cent of Canadian adolescents consumed cannabis in Grade 8. By Grade 12, that percentage nearly tripled to 29 per cent. Early-onset cannabis use has been linked to further drug abuse problems later in life.

The new study, done by UdM doctoral student Charlie Rioux under the supervision of professors Natalie Castellanos-Ryan and Jean Séguin, shows just how much.

The researchers looked at data for 1,030 boys in the Montreal Longitudinal and Experimental Study of white francophones from some of the city’s impoverished neighbourhoods begun in the early 1980s. Every year between ages 13 and 17, the boys were asked if they had consumed cannabis at all in the previous year.

At 17, and again at 20 and 28, they were asked not only whether they consumed cannabis, but also other drugs, including hallucinogens, cocaine, amphetamines, barbiturates, tranquilizers, heroin and inhalants. Then the data were correlated with the age at which they started using cannabis.

Double the chance if frequent use

The results confirmed the researchers’ suspicions: the younger they started, the more likely the boys had a drug problem later as young men. This is partly explained by the frequency with which they consumed cannabis and other drugs, but those who started before age 15 were at higher risk regardless of how often they consumed.

“The odds of developing any drug abuse symptoms by age 28 were non-significant if cannabis use had its onset at ages 15 to 17, but were significant and almost doubled each year if onset was before age 15,” the study says. Even if those who start smoking cannabis at 17 years were at lower risk, frequent users (20 or more times a year) at age 17 had almost double the chance of abuse by age 28 than occasional users.

And that may be underestimating the problem, the researchers say.

“Notably, considering that the potency of cannabis products increased over the last two decades and that [inthis study] adolescent cannabis use was assessed from 1991 to 1995, it is possible that the higher content of Δ-9-tetrahydrocannabinol in the cannabis available today would be associated with higher rates of drug abuse symptoms.”

Gangs, thievery, drinking

The researchers also found that the earlier that boys were involved in gangs, drank alcohol, got into fights, stole or vandalized property, the earlier they used cannabis and the higher their odds of having drug abuse issues by 28. Those who started drinking at 17 also were at higher risk of having an alcohol problem at 28.

The finding that starting pot smoking between ages 13 and 15 increases the odds of developing a drug problem later on makes it all the more important to prevent or reducing cannabis use as early as possible, the researchers say.

“It may be important to implement these programs by the end of elementary school to prevent early onset of cannabis use,” said Rioux. “Since peer influence and delinquency were identified as early risk factors for earlier cannabis onset and adult drug abuse, targeting these risk factors in prevention programs may be important, especially since prevention strategies working on the motivators of substance use have been shown to be effective.”

Abstract of the study:

The present study examined 1) whether the associations between cannabis use (CU) age of onset and drug abuse by 28 y remain when controlling for risk factors in childhood, adolescence and early adulthood; and 2) the developmental pathways from early risk factors to drug abuse problems. Participants from a longitudinal sample of boys of low socioeconomic status (N = 1,030) were followed from 6 to 28 y. We examined the self-reported CU onset between the ages of 13 and 17 y and drug abuse symptoms by 28 y. The odds of developing any drug abuse symptoms by 28 y were reduced by 31% for each year of delayed CU onset (OR = 0.69). Cannabis, alcohol and other drug frequency at 17 y mediated this association. Still, even when taking that frequency of use into account, adolescents who started using cannabis before 15 y were at a higher risk of developing drug abuse symptoms by age 28 y. Significant indirect effects were found from early adolescent delinquency and affiliation with deviant friends to drug abuse symptoms at 28 y through CU age of onset and substance use frequency at 17 y. The results suggest more clearly than before that prevention programs should aim at delaying CU onset to prevent or reduce drug abuse in adulthood. Furthermore, prevention programs targeting delinquency and/or affiliation with deviant friends in childhood or early adolescence could indirectly reduce substance abuse in adulthood without addressing substance use specifically.

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