Why the adolescent brain is sensitive to psychosis-inducing effects of cannabis

kaleidoscope, vision, cannabis to the brain

According to David A. Lewis, MD, who spoke at the American Psychiatric Association Institute on Psychiatric Services on October 31 in San Francisco, California, impairment in working memory is a key finding in schizophrenia, and this impairment is present before onset of psychosis, persists during the illness, and helps predict functional outcome. Furthermore, research in post-mortem brains and animal models shows that layer 3 of the dorsolateral prefrontal cortex is crucial to working memory.

In a lecture titled “Developmental trajectories in cortical circuits: Identifying sensitive periods for the emergence of schizophrenia,” Dr. Lewis, director of the Translational Neuroscience Program and chair of the department of psychiatry at the University of Pittsburgh, described research that has begun to explain why schizophrenia tends to strike people in late adolescence and early adulthood. A circuit consisting of pyramidal cells and inhibitory GABAergic cells, which is recorded electrophysiologically as the “gamma oscillation,” matures during childhood and early adolescence. In this complex process, which involves GABA, NMDA and cannabinoid receptors, some synapses are strengthened and others pruned. During this “sensitive period,” as Lewis called it, exposure to environmental insults can have a profound effect. One manifestation is that people with schizophrenia end up with 20% fewer dendritic spines, which are post-synaptic structures, on the pyramidal cells in cortical layer 3 than unaffected people.

Epidemiologic data consistently show that youth who use marijuana before 16 years of age double or triple their risk for developing schizophrenia. Tetrahydrocannabinol (THC), which binds to cannabinoid receptors on pyramidal and GABAergic neurons in the cortex, affects visual working memory in many people who use it. In an effort to mimic human teenagers’ regular use of marijuana, Dr. Lewis’ lab gave a group of young rhesus monkeys frequent doses of THC. Compared to non-exposed peers, monkeys who had a 6-month exposure to THC developed impairments in spatial working memory similar to enduring deficits exhibited by humans with schizophrenia. The researchers also looked at a second cognitive task that targets object working memory, which depends upon the ventral prefrontal cortex, an area of the brain that matures earlier. This function was unaffected by exposure to THC.

Dr. Lewis emphasized that timing is crucial and may help explain why certain exposures or traumas have major impact at one time in development and minor impact at another. The impact of treatments likewise may vary by developmental stage, and he said that those that aren’t targeted and timely may have unintended consequences.

(Photo: flickr.com/pt3rmin4t0r)

1 thought on “Why the adolescent brain is sensitive to psychosis-inducing effects of cannabis

  1. Aren’t the majority of teenagers trippers anyway- anywhere from 12 to 25-26- i call teenagers- there all trying to see /feel/see how they fit in- connect in the world- socially and mentally/emotionally— or even if they do- so if anyone’s going to spin out- or get even more insecure- its always going to be this group- and especially on gunga- the truth drug- the magnifying drug- with the whole three drug types in it- plus most of them have already interfered with the development of their brains through alcohol- the burying drug- its all understandable to me- and if anyone is spinning out- or psychosed- its not necessarily because they’re mad- or all of a sudden had some –sleeping dormant insanity– creep up on them- that was always going to be there- and that were going to call, schizophrenia- or if were not, too sure,- schizo- effective- to me these are all normal responses- completely understandable reactions- especially to mind alterers- in a teenage constantly altering- “who the #$%@ am I brain- which to me is just a brain that lacks maturity- or understanding-awareness- because without those ingredients- insecurity takes over- not madness- or schizophrenia- and stopping that to me is in explaining that- not pointing to it- or at it- them- and then acting like a wally about- it- or a drugging terrorist- when it is an insecurity that all teenagers get – some more- some less- and when it was born out of – and from — the effects of alcohol- plus additional magnifying mind altering drugs- to begin with- then its obviously a developmental issue- like all thinking conditions- though is coupled with an adverse drug effect– but instead of being real about that- or even pretending that- that’s what it is- just out of not being a misery- or out of- we auto go good- before we go bad- rather than imagining something else- called misery view- its like hey we’ve worked out – mind alterers have adversely effected this person- so instead of focusing on educating them- eliminating the offending drugs from their bodies and minds-and helping them with their drug effected thinking- to overcome this temporary- drug effected condition- in this very insecure teenager- were going to get on the gravy train with our drugs- call them a name – and drug that name into them with our drugs- and their condition causing elements- and chemicals- and well just keep on doing that- because we dont work on people being OK – and wear blinkers for that premise- we work on sick- and proceed from there- with blinkers- anyway just had to say- im sure some of the named have real fairdinkum mind illnesses– but just as im equally sure- a lot of them don’t either- but now have because their expert carers- say they do- and forcefully drug them with drugs that have up too 2000 reported and known adverse side effects in them- so easy to say or call names to anyone when you’ve got 2000 effects going into them- when its just as equally hard to claim- you aren’t mad- when 2000 effects are being forced into you- as well.

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