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"Youth and Marijuana: Is it as
Harmless as we Like to
Think?"
Elizabeth A. Osuch, M.D.
Rea Chair of Affective & Anxiety Disorders
Department of Psychiatry
Schulich School of Medicine & Dentistry
Founder and Physician Lead: First Episode Mood and
Anxiety Program (FEMAP), LHSC
Outline
The MJ situation in Canada and Ontario
 Youth and the brain
 Chemical facts about MJ
 Ways that MJ is problematic

Direct effects on behaviour and brain function
 Effects on thinking and decision making
 Distortion of reward-processing in the brain

WHO
2011
Ontario youth marijuana use rates
Outline
The MJ situation in Canada and Ontario
 Youth and the brain
 Chemical facts about MJ
 Ways that MJ is problematic

Direct effects on behaviour and brain function
 Effects on thinking and decision making
 Distortion of reward-processing in the brain

The Human Brain and
Adolescence
Why are teens and young adults so moody
and impulsive?
How does this relate to drug use/abuse?
How the Brain Works

The brain can be divided into two major
functions


The emotional brain
The thinking (cognitive) brain
How the Brain Dictates our
Behavior

Two routes to action
1)
2)
Emotions first—bottom up—instinctive;
automatic; involves drives, impulses and
basic biological needs; often not conscious.
Emotional processes prevail
Thoughts first—top down—conscious
control; choice; involves planning, delaying
gratification, deciding whether or not to act
on drives, impulses, emotions, or biological
needs. Rational thoughts prevail (related to
what we call executive functioning)
Top Down:
Prefrontal cortex
regulates emotions
Bottom up:
Emotions arise
from limbic system
Executive Function

A major job of the frontal cortex
Planning for the future
 Error recognition and correction
 Stopping and starting actions
 Modulation of impulses
 Abstract reasoning
 Perseverance in the face of obstacles

Sound like things you might need to succeed in
secondary or post-secondary education?
“The dorsal lateral prefrontal cortex, important for
controlling impulses, is among the latest brain
regions to mature without reaching adult
dimensions until the early 20’s.”
“It is argued that adolescence is a period of heightened vulnerability to
risk taking because of a disjunction between novelty and sensation
seeking (which increase dramatically at puberty) and the development
of self-regulatory competence (which does not fully mature until early
adulthood).
“This disjunction is biologically driven, normative, and
unlikely to be remedied through educational interventions
designed to change adolescents’ perception, appraisal, or
understanding of risk.
“Interventions should begin from the premise that
adolescents [and young adults] are inherently more likely
than [older] adults to take risks, and should focus on
reducing the harm associated with risk-taking behavior.”
Brain development

Brain development affects drug use (by
increasing risk taking and experimentation
during adolescents/young adulthood)
In addition, it turns out that…

Drug use affects brain development
“Evidence…indicates that exposure to phytocannabinoids
during the prenatal period, in addition to the adolescent
period, can alter the temporally ordered sequence of events
that occur during neurotransmitter development, in addition
to negatively impacting neural cell survival and maturation.
“Exposure to marijuana during pregnancy might impact
negatively on brain structure in the first years of postnatal
life. Furthermore, early-onset (before age 17) marijuana
use might also have damaging effects on brain
composition.”
So…

Adolescents and young adults are more likely
to be controlled by emotional drives than by
cognitive reasoning, compared with how they
were when younger or how they will behave
as older adults.

It is often harder for youth to “think their way
out” of emotional states and drives, including
boredom, drug craving or other discomfort.

By using MJ regularly during adolescents,
youth are at risk to impair the normal
development of their brains likely including
the prefrontal cortex.
Why do youth use marijuana?
Thrill seeking: Euphoria, sensory distortion,
escape from boredom
Peer Pressure
Why do youth use marijuana?
Emotion regulation – Relief from anxiety,
depression or other uncomfortable states
(boredom)
Outline
The MJ situation in Canada and Ontario
 Youth and the brain
 Chemical facts about MJ
 Ways that MJ is problematic

Direct effects on behaviour and brain function
 Effects on thinking and decision making
 Distortion of reward-processing in the brain

The delta-9-tetrahydrocannabinol (THC)
and cannabidiol (CBD) difference
THC: more means more “stoned”
1)impairs reaction on movement and responseinhibition tasks
2)causes acute psychotic symptoms
THC
3)destabilizes brain function
CBD: more means more stable CBD
1)does not impair performance or induce
CBD
psychosis
THC
2)appears to reduce anxiety
3)stabilizes brain function
MJ from the 1960’s
The delta-9-tetrahydrocannabinol (THC)
cannabidiol (CBD) balance
CBD
THC
THC
CBD
MJ today (wheelchair weed)
MJ from the 1960’s
8.0
THC_mean
6.0
4.0
2.0
0.0
1975
1980
1985
1990
1995
2000
Year
Concentration of THC (in %) in marijuana confiscated by police
in London, Ontario over 25 years
Effective THC concentrations in
2010 are often between 20 and 30%.
THC concentrations in 2010 may be
between 20 and 30%.
“We have found that tobacco increased the amount of
THC inhaled per gram of cannabis from 32.70 2.29
mg/g for a 100% cannabis cigarette to 58.90 ± 2.30 mg/g
for a 25% cannabis cigarette. This indicates that tobacco
increases the vaporization efficiency of THC by as much
as 45% under the conditions tested.”
Outline
The MJ situation in Canada and Ontario
 Youth and the brain
 Chemical facts about MJ
 Ways that MJ is problematic

Direct effects on behaviour and brain function
 Effects on thinking and decision making
 Increases risk for psychiatric disorders
 Distortion of reward-processing in the brain

MJ use impairs how your brain works,
even after 25 days of abstinence
Marijuana use impairs thinking,
even after 25 days of abstinence
Marijuana use impairs thinking,
even after 25 days of abstinence
“These findings indicate that the MJ users may be
hypersensitive to immediate rewards, less sensitive to
losses or negative consequences, and slow to learn
from previous mistakes.”
“The cannabis users, compared to both control groups,
had deficits on verbal fluency, visual recognition, delayed
visual recall, and short- and long-interval prospective
memory…. These findings suggest that cannabis use
leads to impaired executive function.”
Signs of marijuana use
Aggressive Behaviour
 Hallucinations
 Lack of Motivation

Regular marijuana use in
adolescence increases the risk for
schizophrenia
Performing a meta-analysis of 7 prospective studies:
“The pooled odds ration was 2.1 and could not be
explained by confounding [variables] or reverse
causality. Evidence suggests that cannabis is a
component cause in the development and prognosis
of psychosis.”
“Methods: In a longitudinal study of a representative birth cohort
followed to adulthood [for over 20 years], we tested why cannabis use
is associated with the emergence of psychosis in a minority of users,
but not in others.”
“Results:….. Carriers of the COMT valine[158] allele were more
likely to exhibit psychotic symptoms and to develop schizophreniform
disorder if they used cannabis. Cannabis use had no such adverse
influence on individuals with two copies of the methionine allele.”
THC concentrations in 2010 are
generally between
20 and 30%.
“Our most striking finding is that patients with a first
episode of psychosis preferentially used high-potency
cannabis preparations of the sinsemilla (skunk) variety.
In south-east London this form of cannabis is estimated
to contain between 12% and 18% delta-9-THC and less
than 1.5% cannabidiol. In contrast, those in the control
group who used cannabis were more likely to consume
resin (hash), with an average delta-9-THC concentration
of 3.4% and a similar proportion of cannabidiol.”
Marijuana use increases the risk for
mania
“Use of cannabis at baseline increased the risk for manic symptoms
during follow-up (adjusted OR 2.70), adjusted for age, sex, educational
level, ethnicity, single marital status, neuroticism, use of other drugs, use
of alcohol, depressive symptoms and manic symptoms at baseline.
The association between cannabis use and mania was independent of the
prevalence and the incidence of psychotic symptoms.
There is no evidence for reverse causality, as manic symptoms at baseline
did not predict the onset of cannabis use during follow-up (OR 0.35).”
Regular marijuana use increases
the risk for mood disorders
“After adjustment for strong confounders, any use of
cannabis at baseline predicted a modest increase in the
risk of a first major depression (OR 1.62) and a stronger
increase in the risk of a first bipolar disorder (OR 4.98).
The risk of ‘any mood disorder’ was elevated for weekly
and almost-daily users.”
Marijuana use in youth is associated with
decline in cognitive function (IQ)
Longitudinal study from birth to age 38 years. Meier et al., “Persistent
cannabis users show neuro-psychological decline from childhood to
midlife”. Proc Natl Acad Sci USA (2012); 2;109(40):E2657-64.
Participants were from the Dunedin Multidisciplinary
Health and Development Study in Dunedin, New Zealand
(N=1037)
Age at time of study
7-13
years
18
years
21
years
26
years
32
years
38
years
Marijuana use in youth is associated
with decline in cognitive function (IQ)
Hypotheses tested:
1) Cognitive Decline hypothesis (prospectively) –
Demonstrated
2) Specificity hypothesis (multiple tests and alternative
explanations) – Demonstrated
3) Education hypothesis – Not shown
4) The “Everyday Cognition” hypothesis (functional
correlates) – Demonstrated
5) Developmental Vulnerability hypothesis – Demonstrated
6) Recovery hypothesis – Not shown for adolescent users
Marijuana use in youth is associated with
decline in cognitive function (IQ) over time
Meier et al., “Persistent cannabis users show neuropsychological
decline from childhood to midlife”. Proc Natl Acad Sci USA (2012);
2;109(40):E2657-64.
Developmental vulnerability hypothesis:
Meier et al., “Persistent cannabis users show neuropsychological
decline from childhood to midlife”. Proc Natl Acad Sci USA (2012);
2;109(40):E2657-64.
“In fact, adult-onset cannabis users did not
appear to experience IQ decline as a function
of persistent cannabis use….”
“…cessation of cannabis use did not fully
restore neuropsychological functioning among
adolescent-onset former persistent cannabis
users.”
How MJ affects motivation
Perhaps the most frequent problem I see in
my clinical psychiatry practice with youth
who use MJ regularly—impairment in
reward processing.
Normal (before addictive drugs) RewardProcessing “meter”
Athletic/physical
Listening to achievement Good times with
great music
friends/family
Great sex in a great
relationship
Enjoying a
fine meal
Succeeding at
something
you’ve worked long
and
hard for
Enjoying a
beautiful sunset
0
Fun/Enjoyment
Meter
Reward-Processing “meter” after use of
addictive drugs (e.g., marijuana)
Athletic/physical
Listening to achievement Good times with
great music
friends/family
Smoking
dope
Great sex in a
great relationship
Enjoying a
fine meal
Succeeding at
something
you’ve worked long
and
hard for
Enjoying a
beautiful sunset
0
Fun/Enjoyment
Meter
Reward-Processing “meter” after use of
addictive drugs—over time
Athletic/physical
Listening to achievement Good times with
great music
friends/family
Smoking
dope
Taking “e”
Popping
Great sex in a oxys
Enjoying a
fine meal
great relationship
Succeeding at
Smoking
something crack
you’ve worked long
and
hard for
Enjoying a
beautiful sunset
0
Fun/Enjoyment
Meter
Take-home Messages
1)
2)
3)
Youth are at greater risk for and from MJ
abuse than adults
Regular MJ use in youth increases the
risk for several psychiatric disorders
How MJ affects motivation is one of the
problematic aspects of its use
Also, some non-psychiatric concers
with MJ use….
Impaired driving
Lung & cancer problems
“In this study, ammonia was found in mainstream marijuana smoke at
levels up to 20-fold greater than that found in tobacco.
Hydrogen cyanide, NO, NO[x], and some aromatic amines were found
in marijuana smoke at concentrations 3-5 times those found in tobacco
smoke.
Mainstream marijuana smoke contained selected polycyclic aromatic
hydrocarbons (PAHs) at concentrations lower than those found in
mainstream tobacco smoke, while the reverse was the case for
sidestream smoke, with PAHs present at higher concentrations in
marijuana smoke.”