Effects on Youth

Effects of THC on the bodyDownload

Is marijuana addictive for teens?

Dr. Christine Miller

Yes, 17% of those who began their use in adolescence become addicted, and up to about 50% of
those who become daily users end up with addiction:


Obvious withdrawal symptoms are experienced when heavy users cease their habit:

How long the most obvious symptoms of withdrawal last can be found here:

The risk of persisting marijuana use is greater if the product is high in THC concentration:

To understand how many teens this may affect, in 2019, 22% were using at least monthly by the
the time they reached 12th grade:


And 6.4% were using daily:

In the U.S., dependence on marijuana has increased more than dependence on any other drug:

Association of high-potency cannabis use with mental health and substance use in adolescents.  After adjustment for age at onset of cannabis use or for early adolescent measures of psychopathologic conditions and frequency of cannabis use, as compared to lower-potency cannabis users high-potency cannabis in 141 participants was associated with:

  • increase by 4-fold the likelihood of frequent cannabis use,
  • a 10-fold increase in cannabis use problems (i.e. memory problems, smoking before midday, smoking alone, unsuccessful attempts to quit, etc.), and
  • a nearly 2-fold increase in experiencing generalized anxiety disorder.

Associations of Parental Marijuana Use With Offspring Marijuana, Tobacco, and Alcohol Use and Opioid Misuse

November 22, 2019

Conclusions and Relevance In this cross-sectional study, parental marijuana use was associated with increased risk of substance use among adolescent and young adult offspring living in the same household. Screening household members for substance use and counseling parents on risks posed by current and past marijuana use are warranted.

What are some of the ways in which marijuana influences adolescent brain development?

Dr. Christine Millner

The best studies are those that follow the same individuals over time (longitudinal), so they know
the baseline starting point for each person.
For microstructural effects on white matter in the brain:

For effects on brain connectivity:
The superior frontal gyrus is thought to be important for higher cognitive functions and working

For the science on IQ decrements:
and cognitive impairment:

At what age can the brain be considered fully mature?

Dr. Christine Miller

The late twenties:

What are some of the psychological symptoms that adolescents might try to treat with
marijuana, and does it help (e.g. anxiety, depression, ADHD)?

Dr. Christine Miller

The ability of a drug to transiently exert an effect that causes a person to essentially forget about
negative symptoms they are experiencing is important to distinguish from the drug’s long-lasting impact.
As a case in point, it is commonly thought that using marijuana reduces anxiety by making you more relaxed. While that can be a short-term effect, the long-term impact can be quite the opposite:
anxiety or outright panic becomes worse, almost uniformly during intervals between uses

(withdrawal effects):
and in many individuals, even while using:
as confirmed by administering THC in the clinic:
Marijuana use has been shown to double the risk for depression in a rigorous study of twins:
With respect to Attention Deficit Hyperactivity Disorder (ADHD), this may be the sole example of a
well-studied behavioral disorder which generally precedes marijuana use, not vice versa. It is widely acknowledged that ADHD makes substance use of all kinds more likely:

and that the gateway model of drug use is accelerated in those with ADHD:
It is worth noting that the stimulant drugs used to treat ADHD may play a role in susceptibility to substance abuse if treatment is commenced in the teens (rather than earlier) as discussed in this review article (“initiation of stimulant medication (methylphenidate in particular) for ADHD during
adolescence may have negative consequences with respect to later SUD”):

Although rigorous studies of marijuana’s impact on ADHD symptoms are difficult to find in the literature, it has been reported that marijuana-using youth and young adults with ADHD exhibit
more severe symptoms:



New research finds “cannabis is indeed having some sort of an effect on this neuro-maturation process.”

SINCE THE SIZZLING FRIED EGG in the iconic 1987 Partnership for a Drug-Free America ad, we’ve been asked to think about what a “brain on drugs” looks like. Now, we have a slightly better idea, thanks to a study that used MRI scans of adolescent brains at 14 and again at 18 to paint a picture of one plausible effect of marijuana.

In the JAMA Psychiatry report published Wednesday, that effect boiled down to this: accelerated thinning of parts of the brain called the right and left prefrontal cortices.

The authors write that their study is the “largest longitudinal neuroimaging study of cannabis use to date” and is particularly pertinent because of what we know about adolescent cannabis use: Most people trying marijuana for the first time (78 percent) are between the ages of 12 and 20.

“What we found was that the more cannabis use, that people were reporting, from 14 to 19, the faster certain cortical areas were thinning,” lead author Matthew Albaugh tells Inverse. Albaugh is a clinical psychologist and assistant professor of psychiatry at the Larner College of Medicine at the University of Vermont.

The findings, he says, “might suggest that cannabis is indeed having some sort of an effect on this neuro-maturation process.”