A new report published in the online edition of Tobacco Control reveals that nearly £2.5 billion is spent every year in Britain for the care of people with mental health issues who also smoke.
The total costs are more or less equally divided among losses sustained from premature death, lost productivity, and healthcare costs to treat smoking related diseases in this group.
As the prevalence of smoking is around 50% higher among people with mental health issues than among the general public, much more needs to be done to help them quit and stave off this huge financial and personal deficit, conclude the researchers.
They base their findings on an estimate of the avoidable costs of smoking among people with mental health issues in the UK in 2009-10, which they calculated using the World Health Organization's economics of tobacco toolkit.
This assesses the costs of the health effects of cigarette smoking, to include direct healthcare costs, indirect morbidity costs - productivity loss due to excess absenteeism - and indirect mortality costs - productivity loss due to premature death due to smoking related diseases, such as lung cancer, heart disease and stroke, and chronic obstructive pulmonary disease (COPD).
Mental health services account for around 14% of the total annual NHS budget and comprise the single largest component of NHS expenditure, while the ill health caused by smoking costs the NHS more than £5 billion or around 5% of the total annual NHS budget.
An estimated 3 million adults with neurotic and psychotic disorders were smokers in 2009-10. The direct medical cost to the NHS of treating them for diseases caused by smoking amounted to £719 million in 2009-10 - equivalent to £320 per person - considerably higher than the figure for a member of the general public, say the researchers.
They also calculated that productivity losses due to smoking-related diseases amounted to an estimated £823 million for workplace absenteeism and £797 million as a consequence of premature death.
"It is clear that smoking in people with mental [health] disorders in the UK imposes a significant economic burden and therefore that the development and implementation of interventions to stop smoking in this group should be a high priority," the researchers write.
"This economic case augments the ethical and clinical imperative of dealing with smoking more systemically and effectively in this group, and is over and above the health benefits of improved quality and quantity of life," they add.