Thursday, May 31, 2012

Cannabis, teenagers and schizophrenia


Cannabis or marijuana use by teenagers and adolescents is highly associated with the onset of psychosis and schizophrenia. Cannabis goes by many names including hash, pot, grass, weed, or ganja. This gateway drug is falsely thought to be innocuous and as having no lasting effects. Cannabis use by teenagers is often not recognised as a problem. Cannabis is cheap and easily accessible in most student populations. Pune is a major hub for the cannabis drug trade. This week a quarter tonnne of ganja was found dumped in a well. Cannabis use is rampant in Pune colleges and hostels, where students assiduosly guard and maintain their 'stash'. During the 57th National School Games the highest number of students testing positive for marijuana came from Maharashtra.

Regular cannabis use increases the risk for schizophrenia and psychosis by upto 4 times. There is increasing evidence that cannabis use can precipitate schizophrenia in vulnerable individuals. This is especially so with early onset use of cannabis. Cannabis also exacerbates symptoms of schizophrenia in those who have already developed the disorder. Psychotic disorders like schizophrenia involve disturbances in the dopamine neurotransmitter systems of the brain. Δ9-tetrahydrocannabinol (THC) - the key neurochemical in cannabis - interacts with dopamine to adversely affect its functioning by multiple mechanisms.

Teenagers are especially vulnnerable to the schizophrenia-inducing effects of cannabis. Cannabis like substances (anandamide) called endocannabinoids, produced by the body, play an important role in several processes of brain maturation. Regular marijuana use affects this process of brain maturation in teenagers. Schizophrenia is also a disorder of brain maturation. Disruption of the endocannabinoid system in the adolescent brain by exposure to cannabis interferes with brain maturation. This provides a mechanism to increase the risk for development of schizophrenia in adolescence.

How to cut down and stop cannabis use

  1. Write down a list of reasons for wanting to stop - you will need to review this at times when you are feeling low or experiencing craving.
  2. Tell someone you trust that you are quitting
  3. Get rid of the paraphernelia for smoking cannabis - the stash, wrappers, lighters, matches. You may be surprised at the number of places where small amounts are hidden. Get rid of it all.
  4. Take measures to prevent fresh procurements - avoid places and people associated with replenishments
  5. Make a list of things to do to occupy the time freed-up from procuring and using cannabis.
  6. Review your list of reasons and things to do when you feel low and when craving is intense.
  1. Paola Casadioa, Cathy Fernandesb, Robin M. Murray, Marta Di Forti. Cannabis use in young people: The risk for schizophrenia.  Neuroscience & Biobehavioral Reviews. Volume 35, Issue 8, August 2011, Pages 1779–1787. doi:10.1016/j.neubiorev.2011.04.007
  2. Degenhardt L, Hall W. Is cannabis use a contributory cause of psychosis? Can J Psychiatry. Aug 2006;51(9):556-65.
  3. Deepak Cyril D’Souza,Richard Andrew Sewell,and Mohini Ranganathan. Cannabis and psychosis/schizophrenia: human studies. Eur Arch Psychiatry Clin Neurosci. 2009 October; 259(7): 413–431. Published online 2009 July 16. doi: 10.1007/s00406-009-0024-2


  1. You said that marijuana increases the risk of schizophrenia and psychosis, but couldn't it be the other way round? It could be that people with schizophrenia and psychosis would be attracted to cannabis to self medicate? These are people who wouldn't trust psychiatrists, so they use cannabis.

    This is like saying that smoking increases chances of depression, simply because people who are depressed are more likely to smoke.

  2. No, the reverse direction does not hold. Several long-term follow-up studies excluded people with psychosis at baseline, so the observed association between cannabis and psychosis is unlikely to reflect reverse causation.

    Moore TH, Zammit S, Lingford-Hughes A, Barnes TR, Jones PB, Burke M, Lewis G. Cannabis use and risk of psychotic or affective mental health outcomes: a systematic review. Lancet. 2007 Jul 28;370(9584):319-28.

    Also check this recent MRI study which highlights the cognitive differences in schizophrenia patients who used cannabis vs those who did not.

    Else-Marie Løberg1, Merethe Nygård1, Jan Øystein Berle, Erik Johnsen, Rune A. Kroken, Hugo A. Jørgensen and Kenneth Hugdahl1. An fMRI study of neuronal activation in schizophrenia patients with and without previous cannabis use. Front. Psychiatry, 30 October 2012 | doi: 10.3389/fpsyt.2012.00094

  3. If cannabis were all that bad, how come it is legal in Netherlands and now in the US in the states of Colorado and Washington?

    There is no significant increase in Danish schizophrenia compared to the rest of Europe. (We will have to wait for US data)

    Finally that fMRI paper abstract concludes, "It is concluded that the present study show some differences in brain activation to a cognitively challenging task between previous cannabis and no-cannabis schizophrenia patients." Hardly news to stop the presses, it is called being stoned.

    1. The reason why any government would legalise cannabis use is best answered by that government and its citizens. In the US cannabis use is legal for medical reasons on a doctor’s prescription. However, the US judicial system is now questioning this decision to legalise medical use of cannabis.

      Your statement that there is no increase in schizophrenia in the Netherlands is incorrect. The Netherlands Mental Health Survey and Incidence Study showed cannabis use significantly increased the risk for psychosis in that population.

      None of the subjects in the fMRI study were on cannabis at the time of fMRI. The article title itself tells you authors studied schizophrenia patients with and without previouscannabis use. A reading of the full text will tell you “Exclusion criteria were ... substance abuse within the past 6 month (except two patients who had used cannabis twice the last 6 months ...)”. So yes, they were ‘stoned’, but the cognitive impairments demonstrated were not a result of current cannabis intake; but a result of persistent difference in brain function in people who had previously used cannabis.

  4. sir when ever i use the grass i generally get a faster heartbeat i feel like i will die ..i couldnt enjoy the trip ...why it happens ???
    what is the reason for the faster heartbeat ?

    1. You have Cannabis-Induced Anxiety Disorder.
      Some users experience panic after using cannabis, especially when they use more potent forms of cannabis.

      The faster heartbeat is due to the direct action of cannabis on the heart. This causes the heart rate to increase by 20-50% within minutes of smoking cannabis. Changes in blood pressure also occur. A sudden change in posture from from lying down to standing up may produce light-headedness and faintness. All these factors increase feelings of panic.


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