{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,17]],"date-time":"2026-10-17T01:32:32Z","timestamp":1792200752512,"version":"4.4.0"},"reference-count":55,"publisher":"Royal College of Psychiatrists","issue":"2","license":[{"start":{"date-parts":[[2019,9,17]],"date-time":"2019-09-17T00:00:00Z","timestamp":1568678400000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/www.cambridge.org\/core\/terms"}],"content-domain":{"domain":["cambridge.org"],"crossmark-restriction":true},"short-container-title":["Br J Psychiatry"],"published-print":{"date-parts":[[2021,2]]},"abstract":"<jats:sec id=\"S0007125019002022_sec_a1\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>There is increasing evidence that smoking is a risk factor for severe mental illness, including bipolar disorder. Conversely, patients with bipolar disorder might smoke more (often) as a result of the psychiatric disorder.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"S0007125019002022_sec_a2\">\n                    <jats:title>Aims<\/jats:title>\n                    <jats:p>We conducted a bidirectional Mendelian randomisation (MR) study to investigate the direction and evidence for a causal nature of the relationship between smoking and bipolar disorder.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"S0007125019002022_sec_a3\" sec-type=\"methods\">\n                    <jats:title>Method<\/jats:title>\n                    <jats:p>We used publicly available summary statistics from genome-wide association studies on bipolar disorder, smoking initiation, smoking heaviness, smoking cessation and lifetime smoking (i.e. a compound measure of heaviness, duration and cessation). We applied analytical methods with different, orthogonal assumptions to triangulate results, including inverse-variance weighted (IVW), MR-Egger, MR-Egger SIMEX, weighted-median, weighted-mode and Steiger-filtered analyses.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"S0007125019002022_sec_a4\" sec-type=\"results\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Across different methods of MR, consistent evidence was found for a positive effect of smoking on the odds of bipolar disorder (smoking initiation OR\n                      <jats:sub>IVW<\/jats:sub>\n                      = 1.46, 95% CI 1.28\u20131.66,\n                      <jats:italic>P<\/jats:italic>\n                      = 1.44 \u00d7 10\n                      <jats:sup>\u22128<\/jats:sup>\n                      , lifetime smoking OR\n                      <jats:sub>IVW<\/jats:sub>\n                      = 1.72, 95% CI 1.29\u20132.28,\n                      <jats:italic>P<\/jats:italic>\n                      = 1.8 \u00d7 10\n                      <jats:sup>\u22124<\/jats:sup>\n                      ). The MR analyses of the effect of liability to bipolar disorder on smoking provided no clear evidence of a strong causal effect (smoking heaviness beta\n                      <jats:sub>IVW<\/jats:sub>\n                      = 0.028, 95% CI 0.003\u20130.053,\n                      <jats:italic>P<\/jats:italic>\n                      = 2.9 \u00d7 10\n                      <jats:sup>\u22122<\/jats:sup>\n                      ).\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"S0007125019002022_sec_a5\" sec-type=\"conclusions\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>These findings suggest that smoking initiation and lifetime smoking are likely to be a causal risk factor for developing bipolar disorder. We found some evidence that liability to bipolar disorder increased smoking heaviness. Given that smoking is a modifiable risk factor, these findings further support investment into smoking prevention and treatment in order to reduce mental health problems in future generations.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1192\/bjp.2019.202","type":"journal-article","created":{"date-parts":[[2019,9,17]],"date-time":"2019-09-17T03:48:48Z","timestamp":1568692128000},"page":"88-94","update-policy":"https:\/\/doi.org\/10.1017\/policypage","source":"Crossref","is-referenced-by-count":63,"title":["Smoking and the risk for bipolar disorder: evidence from a bidirectional Mendelian randomisation study"],"prefix":"10.1192","volume":"218","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6245-6498","authenticated-orcid":false,"given":"Jentien M.","family":"Vermeulen","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Robyn 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