Effects of Cannabis on theTeenage Brain: Current Findings (Camchong, Lim,…
Effects of Cannabis on theTeenage Brain: Current Findings
Camchong, Lim, & Kumra (2016)
Adverse effects of cannabis on adolescent brain development: A longitudinal study
Hypotheses and aims of the study
1) Determine whether there are differences in in the trajectory of anterior cingulate cortex (ACC; role in self-regulatory mechanisms) across time between adolescents with Cannabis Use Disorder (CUD) and Healthy Controls (HC) -> Prediction that CUD would show a significant drop in connectivity across time compared to HC.
2) Investigate whether baseline functional connectivity measures could be used to predict cannabis use during the interscan interval -> Hypothesized that lower ACC functional connectivity would predict the amount of cannabis use during the observation period.
3)To explore whether the degree of cannabis use during the observation period was related to i) intelligence and ii) executive function -> Hypothesized that higher cannabis use during interscan period would be negatively correlated with measures of intelligence and executive function.
n=65 participants with usable data; 22 CUD (nF =8); 43 HC (nF = 20); 10-21 years old;
MRI at 2 time points baseline and 18 months after study entry
Intelligence and executive functioning metrics: The Weschler Abbreviated Scale of Intelligence (WASI) measure of 3 attentional types (alerting, executive attention, and orienting)
Measure of longitudinal changes in resting function
in functional connectivity networks known to mediate self-regulatroy control (functional connectivity of 5 ACC networks); Assessment of the influence of cannabis use during the interscan interval on functional connectivity.
CUD had a significant decrease in in functional connectivity across time
between caudal ACC and the dorsolateral prefrontal cortex (DLPFC)and Broadmann's Area 10 (SFG) between time points 1 and 2.
Lower functional connectivity
between ACC and orbitofrontal cortex at time 1
predicted more days of cannabis use
during the interscan interval (18 months).
Cannabis consumption during interscan interval predicts IQ at time 2:
greater use predicted low full-scale IQ at time 2
Cannabis consumption during the interscan interval predicts cognitive function at time 2:
Greater cannabis use lead to slower reaction times during ANT performance at time 2; measure of executive control
Observation of adverse effects on adolescent brain maturation in 18 month longitudinal study;
IQ, Executive functioning, cognitive development.
Identification of a potential neural marker of relapse to cannabis use
characterized by lower resting functional connectivity between caudal ACC and and OFC in adolescents with CUD.
Roles of ACC-OFC in decision making is related to behavioural processes altered in addiction;
a disruption in functional connectivity in the 2 regions may indicate a lack of integration of behavioural constructs needed to sustain abstinence/cognitive control (caudal ACC) over learned associations and behaviour (OFC).
Present findings do NOT indicate prefrontal volumetric differences;
cannabis use may have functional as opposed structural implications on the prefrontal cortex.
Fergusson & Boden (2008)
Cannabis use and later life outcomes
Aims of the Study:
Examine the associations between the extent of cannabis use during adolescence and young adulthood and
later education, employment, relationship satisfaction, and life satisfaction outcomes.
of a New Zealand birth cohort studied to 25 years of age.
Cannabis use ages 14-25
University degree attainment by age 25
Income at age 25
Welfare dependence between 21-25 years
Unemployment 21-25 years
Increasing levels of cannabis use between ages 14 and 21 was associated with:
Lower levels of degree attainment by 25
Lower income at age 25
Higher levels of welfare dependence between ages 21 and 25.
Lower levels of life satisfaction
Lower levels of relationship satisfaction
Increasing the use of cannabis in adolescence may result in longer-term educational, economic, and personal disadvantage in young adulthood.
Associations may be explained by residual confounding despite controls for various social factors that have a similar effect as cannabis use and co-morbid mental illneses.
May reflect the consequences of cannabis use on neuropsychological functioning; acute and long term changes in brain structure.
Associations may be social as opposed to biological; i.e. since cannabis is often used in social settings, individuals who use it more frequently my find themselves in settings that discourage educational achievement and material success.
Followed one group of individuals born at a particular time and reared in a specific social context.
Results are based on self-reported data
Study has likely underestimate the extent of cannabis use particularly for those who use it most frequently; estimates presented may be somewhat conservative
Spechler et. al (2015)
Cannabis use in early adolescence: Evidence of amygdala hypersensitivity to signals of threat
Cannabis-using 14 year olds will have different activity in the amygdalae compared to controls in a facial affective processing task.
Study overview: Impact of previous cannabis use (n=70) compared to closely matched controls (n=70) in early adolescents using a face processing task during fMRI.
Epstein & Kumra (2015).
Altered cortical maturation in adolescent cannabis users with and without schizophrenia
Typical adolescent cortical development patterns
Back-to-front direction; heteromodal association cortex (HASC) matures last
HASC = Prefrontal, superior temporal, and inferior parietal cortices.
HASC supports the highest integrative functions of the brain including: working memory, attention, language, and executive function.
Structures are important for the development of emotional regulation and planning that are often lacking in adolescence.
THC may be more deleterious in adolescents as cognitive development and brain maturation are ongoing.
Primary target of exogenous cannabinoids = Cannabinoid-1 (CB-1) receptor; present throughout the brain, including the HASC; part of endocannibinoid system which regulates synaptic plasticity and neural maturation.
Hypotheses + Methodology
1) The magnitude of cortical thinning would be altered for CUD (+) compared to CUD (-) across HASC regions
2) The magnitude of these alterations would be related to the amount of cannabis consumed.
HC without a history of substance use disorders
Treatment-seeking adolescents with CUD
Early-onset schizophrenia without CUD
Early onset schizophrenia with CUD
Cortical attentuation/increased cortical thickness in both non-psychotic and psychotic participants with CUD compared to HC; impacted regions of HASC include:
Left and right superior frontal gyri
Left pars opercularis
Right pars triangularis
Inferior parietal cortex