Highwood Highlights No. 31. October 2009
In this newsletter we are going to focus on the connection between Schizophrenia and the use of street drugs, especially marijuana. The subject has been very well presented and summarised at the following web page, which we would encourage our subscribers to have a look at: http://www.schizophrenia.com/prevention/streetdrugs.html
Some of the scientific studies on this subject are listed at the bottom of this newsletter. From schizophrenia.com, we quote (with light editing): “LSD, methamphetamine, marijuana (a.k.a. hash or cannabis) and alcohol have been linked with significantly increased probability of developing psychosis [i.e. madness or loss of a connection with reality] and schizophrenia. This link has been documented in over 30 different scientific studies (done mostly in the UK, Australia and Sweden) over the past 20 years. In one example, a study [Cannabis and schizophrenia. A longitudinal study of Swedish conscripts, Lancet, 1987] interviewed 50,000 members of the Swedish Army about their drug consumption and followed up with them later in life. Those who were heavy consumers of cannabis at age 18 were over 600% more likely to be diagnosed with schizophrenia over the next 15 years than those did not take it. Experts estimate that between 8% and 13% of all schizophrenia cases are linked to marijuna / cannabis use during teen years.
“Many of these research studies indicate that the risk is higher when the drugs are used by people under the age of 21, a time when the human brain is developing rapidly and is particularly vulnerable.
“Researchers in New Zealand found that those who used cannabis by the age of 15 were more than three times (300%) more likely to develop illnesses such as schizophrenia. Other research has backed this up, showing that cannabis use increases the risk of psychosis by up to 700% for heavy users, and that the risk increases in proportion to the amount of cannabis used (smoked or consumed). Additionally, the younger a person smokes/uses cannabis, the higher the risk for schizophrenia, and the worse the schizophrenia is when the person does develop it. Research by psychiatrists in inner-city areas speak of cannabis being a factor in up to 80 percent of schizophrenia cases.
“Professor Robin Murray (London Institute of Psychiatry) has recently (2005) completed a 15-year study of more than 750 adolescents in conjunction with colleagues at King's College London and the University of Otago in New Zealand.
“Overall people were 4.5 times more likely to be schizophrenic at 26 if they were regular cannabis smokers at 15, compared to 1.65 times for those who did not report regular use until age 18.
“Many researchers now believe that using the drug while the brain is still developing boosts levels of the chemical dopamine in the brain, which can directly lead to schizophrenia.
“Professor John Henry, clinical toxicologist at Imperial College London said research has shown that people with a certain genetic makeup who use the drug face a ten times (1000%) higher risk of schizophrenia.
“The increased risk applies to people who inherit variants of a gene named COMT and who smoked cannabis as teenagers. About a quarter of the population have this genetic make-up and up to 15 per cent of the group are likely to develop psychotic conditions if exposed to the drug early in life. Neither the drug nor the gene raises the risk of psychosis by itself.
“A recent Dutch study showed that teenagers who indulge in cannabis as few as five times in their life significantly increase their risk of psychotic symptoms.
“The increase in evidence during the past decade could be tied to the increased potency of marijuana. A review by the British Lung Association says that the cannabis available on the streets today is 15 times more powerful than the joints being smoked three decades ago.
“Schizophrenia can sometimes be triggered by heavy use of hallucinogenic drugs, especially LSD; but it appears that one has to have a genetic predisposition towards developing schizophrenia for this to occur. There is also some evidence suggesting that people suffering from schizophrenia but responding to treatment can have an episode as a result of use of LSD. Methamphetamine and PCP also mimic the symptoms of schizophrenia, and can trigger ongoing symptoms of schizophrenia in those who are vulnerable.
“Professor Castle, author of the book Marijuana and Madness, has said that those people with this "psychotic proneness" were those who had a family history of mental illness or who had had a bad response on their first use of cannabis or to a tiny amount. Others at risk included those who had experienced a psychotic episode where they had paranoid thinking or heard a voice calling their name. Professor Castle said experiencing such a one-off episode was far more common than people thought.
‘People with such a vulnerability should avoid cannabis like the plague,’ he said.
“Without the effects of the drug, such a person might live their whole life without ever experiencing mental health problems. It has been estimated, for example, that between 8% and 13% of people that have schizophrenia today would never have developed the illness without exposure to cannabis.
“Cannabis impacts on neurotransmitters that regulate how arousal and stress are managed in the brain. Cannabis takes a long time to metabolise, and can quickly build up to high levels in the body. Once you get to this point, there is a real risk of depression or schizophrenia being triggered.
“A Swedish study of 50,000 military conscripts found heavy use of cannabis increased the risk of suicide by four times (400%). A Victorian study of 2332 adolescents found weekly use increased the risk of suicide attempts among females by five times. Weekly use as a teenager doubled the risk of depression and anxiety. Daily use at the age of 20 boosted the risk of depression and anxiety by five times (500%).
Some relevant scientific research on schizophrenia and cannabis:
Update on marijuana, McGuinness TM, J Psychosoc Nurs Ment Health Serv. 2009 Oct; 47(10):19-22. doi: 10.3928/02793695-20090902-03.
Illicit substance use and its correlates in first episode psychosis, Mazzoncini R, et. al., Acta Psychiatr Scand. 2009 Oct 13.
Cannabis and psychosis/schizophrenia: human studies, D'Souza DC, Sewell RA, Ranganathan M, Eur Arch Psychiatry Clin Neurosci. 2009 Oct;259(7):413-31. Epub 2009 Jul 16.
A prospective study of cannabis use as a risk factor for non-adherence and treatment dropout in first-episode schizophrenia, Miller R, et. al. Schizophr Res. 2009 Sep;113(2-3):138-44. Epub 2009 May 28.
Cannabis-induced psychosis and subsequent schizophrenia-spectrum disorders: follow-up study of 535 incident cases. Br J Psychiatry. 2005 Dec;187:510-5
Predictors of schizophrenia--a review. Br Med Bull. 2005 Jun 9;73:1-15. Print 2005.
Cannabis as a risk factor for psychosis: systematic review. J Psychopharmacol. 2005 Mar;19(2):187-94
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Disclaimer: Any medical comments made by Dr. Bird are not to be taken as personal medical advise and are presented for general educational purposes only.
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