喫煙を止めてもう数年経つのだが。
Sarah Boseley “Smoking tobacco might increase risk of schizophrenia, say researchers” http://www.theguardian.com/society/2015/jul/10/smoking-tobacco-might-increase-risk-schizophrenia-say-researchers-psychosis
James MacCabe博士*1を中心とする、キングズ・カレッジ精神医学・心理学・神経科学研究所*2の研究ティームが最近Lancet Psychiatryに発表した論文によると、喫煙は「統合失調症」その他の精神病のリスクを増加せしめる*3。
The researchers found that daily smokers had an increased risk of psychosis. More than half - 57% - of people arriving at mental health services with their first episode were smokers, which is nearly three times the normal occurrence in the population. Smokers experienced psychosis one year earlier than non-smokers.“We can’t say that we have proof that cigarette smoking causes schizophrenia,” said Sir Robin Murray*4, professor of psychiatric research at King’s. “Indeed it is very difficult to point to any particular factor and say it causes schizophrenia. It is a bit like heart disease – there are a number of risk factors. You inherit some vulnerability and … are exposed to various things which increase the risk to your life.”
大麻（canabis）も統合失調症のリスク要因であるとされるが、煙草は大麻よりもリスクが高い；
Cannabis is known to cause psychosis and schizophrenia*5. The authors say they could not be certain that all the studies they looked at had completely accounted for cannabis use. However, they are certain there is a modest effect caused by tobacco alone.
生物学的な説明。ドーパミンと遺伝子；
統合失調症はドーパミンの過剰と関係がある。煙草は、アンフェタミン、コカイン、大麻とともに、ドーパミン分泌を刺戟する。There are biologically plausible reasons why smoking may be linked to psychosis. “Excess dopamine is the best biological explanation we have for psychotic illnesses such as schizophrenia,” said Murray. “It is possible that nicotine exposure, by increasing the release of dopamine, causes psychosis to develop.” A number of other drugs can stimulate dopamine production, including amphetamines, cocaine and cannabis.
There are also genetic clues – a small number of DNA sequences (called SNPs) are known to be implicated in both schizophrenia and smoking.,
そうか。でも鬱病は逆にドーパミンの不足と関係があるわけでしょ*6 。だとすれば、ドーパミン分泌を刺戟する煙草は鬱病に対してはポジティヴに作用し、煙草を吸う人は鬱病のリスクが低くなるのでは？ また、喫煙する人の数は世界的に減少が続いているが、喫煙者数と統合失調症患者数の間には逆相関関係が描けるのだろうか。抗鬱剤の処方数は増えており、抗鬱剤を必要とする人という意味での鬱病患者は増えていることになる*7。
*1:See eg. https://kclpure.kcl.ac.uk/portal/james.maccabe.html
*2:http://www.kcl.ac.uk/ioppn/index.aspx
*3:Pedro Gurillo, Sameer Jauhar, Robin M Murray,and James H MacCabe “Does tobacco use cause psychosis? Systematic review and meta-analysis” http://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366%2815%2900152-2/abstract See also “Smoking cigarettes associated with increased risk of psychosis” http://www.kcl.ac.uk/ioppn/news/records/2015/July/Smokingcigarettesassociatedwithincreasedriskofpsychosis.aspx
*4:See eg. https://kclpure.kcl.ac.uk/portal/robin.murray.html
*5:See Hannah Devlin “Smoking skunk cannabis triples risk of serious psychotic episode, says research” http://www.theguardian.com/society/2015/feb/16/skunk-cannabis-triples-risk-psychotic-episodes-study
*6:See eg. 「非定型うつ病とドパミン」http://ameblo.jp/kyupin/entry-11246512493.html 「うつ(鬱)は精神の弱さではなく神経伝達物質(セロトニン・ドーパミン・ノルアドレナリン)不足で起こる脳の病気！|うつになりやすい傾向度チェック|うつの人に「頑張って」はNGワード！うつの人に言ってはいけない言葉|産後うつの原因は女性ホルモンの減少|駆け込みドクター！〜身近な病気…うつを学ぶ(11/16)」http://currentdiary.seesaa.net/article/409044567.html
*7:Sarah Boseley, Mona Chalabi and Mark Rice-Oxley “Antidepressant use on the rise in rich countries, OECD finds” http://www.theguardian.com/society/2013/nov/20/antidepressant-use-rise-world-oecd Mentioned in http://d.hatena.ne.jp/sumita-m/20131121/1385003012
