• inflammatory bowel disease
• ulcerative colitis
• Crohn’s disease
• appendicitis
• appendicectomy

The endless “genetics or environment” debate can get rather convoluted, whether about inflammatory bowel disease (IBD) or any other complex disease.¹ With regard to IBD, a series of epidemiological and genetic “breakthroughs” have barely inched us closer to clarifying this issue.² Indeed, many decades of research on Crohn’s disease and ulcerative colitis have so far revealed just one principal gene, at the NOD2 locus on chromosome 16,³ and one major environmental factor, smoking,⁴ in influencing susceptibility to either of these conditions.

Currently, the “Crohn’s disease gene” is the hottest topic but environmental issues keep pushing themselves into the picture. The “protective” effects of smoking in ulcerative colitis have been old news for a while,⁵ with its deleterious effects in Crohn’s disease only more recently coming to the fore.⁶ But all of the observations on smoking over the past 20 years have not really helped us very much, despite intriguing hypotheses …