"Youth and Marijuana: Is it as Harmless as we Like to Think?"

Transcription

1 "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

2 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

3 WHO 2011

4 Ontario youth marijuana use rates

5 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

6 The Human Brain and Adolescence Why are teens and young adults so moody and impulsive? How does this relate to drug use/abuse?

7 How the Brain Works The brain can be divided into two major functions The emotional brain The thinking (cognitive) brain

8 How the Brain Dictates our Behavior Two routes to action 1) Emotions first bottom up instinctive; automatic; involves drives, impulses and basic biological needs; often not conscious. Emotional processes prevail 2) 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)

9 Bottom up: Emotions arise from limbic system Top Down: Prefrontal cortex regulates emotions

10 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?

11 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.

12 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).

13 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.

14 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

15 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.

16 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.

17 Why do youth use marijuana? Thrill seeking: Euphoria, sensory distortion, escape from boredom Peer Pressure

18 Why do youth use marijuana? Emotion regulation Relief from anxiety, depression or other uncomfortable states (boredom)

19 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

20 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

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23 The delta-9-tetrahydrocannabinol (THC) cannabidiol (CBD) balance CBD THC THC CBD MJ today (wheelchair weed) MJ from the 1960 s

24 THC_mean Year Concentration of THC (in %) in marijuana confiscated by police in London, Ontario over 25 years

25 Effective THC concentrations in 2010 are often between 20 and 30%.

26 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 mg/g for a 100% cannabis cigarette to ± 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.

27 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

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29 MJ use impairs how your brain works, even after 25 days of abstinence

30 Marijuana use impairs thinking, even after 25 days of abstinence

31 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.

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33 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.

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35 Signs of marijuana use Aggressive Behaviour Hallucinations Lack of Motivation

36 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.

37 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.

38 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.

39 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).

40 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.

41 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):E 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

42 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

43 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):E

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45 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):E 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.

46 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.

47 Normal (before addictive drugs) Reward- Processing meter Enjoying a fine meal Enjoying a beautiful sunset Listening to great music Athletic/physical achievement Good times with friends/family Great sex in a great relationship Succeeding at something you ve worked long and hard for 0 Fun/Enjoyment Meter

48 Reward-Processing meter after use of addictive drugs (e.g., marijuana) Enjoying a fine meal Enjoying a beautiful sunset Listening to great music Athletic/physical achievement Good times with friends/family Smoking dope Great sex in a great relationship Succeeding at something you ve worked long and hard for 0 Fun/Enjoyment Meter

49 Reward-Processing meter after use of addictive drugs over time Enjoying a fine meal Enjoying a beautiful sunset Smoking dope Listening to great music Athletic/physical achievement Good times with friends/family Taking e Popping oxys Great sex in a great relationship Smoking crack Succeeding at something you ve worked long and hard for 0 Fun/Enjoyment Meter

50 Take-home Messages 1) Youth are at greater risk for and from MJ abuse than adults 2) Regular MJ use in youth increases the risk for several psychiatric disorders 3) How MJ affects motivation is one of the problematic aspects of its use

51 Also, some non-psychiatric concers with MJ use.

52 Impaired driving

53 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.