The causal impact of mental health on tobacco and alcohol consumption: An instrumental variables approach

Mental health disorders and addictive behaviours are two public health issues that are estimated to impose significant socio-economic costs to the global economy. Individuals with mental health disorders disproportionally engage in more addictive behaviours such as smoking, drinking, gambling, or using illicit drugs. Addictive behaviours are difficult to manage and even more so for people with mental health problems. To optimize public health interventions and medical treatments it is important to understand whether mental health disorders cause addictive behaviours. The reciprocal relationship between psychiatric and substance use disorders is well-known, yet it remains largely unknown whether mental health morbidity causally leads to addictive behaviours.

We find that mental distress significantly increases the prevalence and intensity of either cigarette or alcohol consumption. Further analysis reveals that mental distress also substantially increases household monetary expenditures on either tobacco or alcohol. The impact is greater for lower educated individuals or children of smokers, and is slightly higher for males.

Our finding of a strong association between life stress events and depression provides an argument for public initiatives that support vulnerable groups to cope with negative psychological events. Such policies may not only reduce the overall prevalence and impact of mental distress but also discourage mental distress-attributable addictive behaviours and hence alleviate their associated socio-economic costs, following our finding of a measurable impact of mental distress on increasing addictive behaviours. Overall, our findings, together with others, highlight the role of mental health screening and treatment programs, especially among lower educated individuals or children of smokers, to assist in the prevention of addictive activities which are costly to both the individual, and to broader society.