A lot of people also die from iatrogenesis too, (medically caused illness)! but all joking apart, smoking is the biggy as regards early deaths.
Zyban side effects, in order of reported frequency, (from the, "British National Formulary,)" dry mouth,gi disturbances, insomnia, tremor, impaired concentration, headache, dizziness, depression, agitation, anxiety, rash, itching, sweating, fever, taste disturbances. Rare reactions include visual disturbances and seizures. "
Sounds like one of my hangovers !