Smoking, a symptom of mental health disorder

Combining the efforts of mental health services and substance abuse specialists could be relevant to enhance the promotion of healthy behavioural patterns and reducing the impact of depression on overall health.

Moreover, smoking might be regarded as a symptom of mental health disorders and a marker of increased risk for depression. Previous studies reported that people who have successfully quit smoking have better emotional and mental health stability and score better in the HRQoL measurements. On the other hand, anti-depressive drugs are used for smoking cessation.

Smoking, psychiatric illness, and the brain

According to an editorial by Patricia Boska, Ph.D., that was published in the Journal of Psychiatry and Neuroscience, smoking is a factor that should regularly be considered as a potential confound in neurobiological studies of psychiatric illnesses. “Smoking can be regarded as playing at least several roles in relation to psychiatric illness — as a causal factor contributing to psychiatric disorders, as an agent causing brain changes on its own that may interact with psychiatric pathophysiology, or as a modulator of effects of psychotropic medications. In each of these roles, smoking may impact the course of psychiatric illness and brain function,” she said.

Smoking and ADHD

“There is strong evidence for an association between smoking and the development or progression of psychiatric disorders at the ends of the developmental timeline — namely, ADHD and Alzheimer’s disease/dementia,” explained Boska in her editorial.

In the case of ADHD, a large body of evidence supports an association between maternal smoking during pregnancy and increased risk for ADHD. However, whether maternal smoking is a causal factor for ADHD remains open to question, with recent research suggesting that the association may be due to a shared familial/genetic susceptibility for both smoking and ADHD.

Nonetheless, children with ADHD born from mothers who smoked during pregnancy have been reported to have more severe behavioural problems than children with ADHD born from non-smoking mothers, with a dose–response relationship between the amount smoked and several cognitive and clinical variables in the children.

 At a neurobiological level, maternal smoking during pregnancy has been shown to be associated with grey matter loss and cortical thinning as well as functional alteration in neural circuitry involved in inhibitory control and reward in children.

Smoking, Dementia and Alzheimer’s disease

There is also strong epidemiological evidence that smoking is associated with an increased risk for dementia and the development of Alzheimer’s disease. In a 2-year longitudinal study of 186 healthy elderly individuals, Durazzo, and colleagues found that the rate of atrophy in several brain regions known to be affected by Alzheimer’s disease was greater in those with a history of smoking than in never-smokers.

Although the precise mechanism by which smoking produces central nervous system (CNS) atrophy has not been pinpointed, it is plausible that these effects may be mediated through the burden of cardiovascular impairment caused by smoking and by the cumulative direct cytotoxic effects of some of the thousands of compounds present in cigarette smoke.

Smoking causes brain changes that affect psychiatric symptoms

With regards to neuropsychological function, short-term administration of nicotine has positive effects on aspects of cognition, including learning, memory, and attention in healthy individuals, as well as in patients with schizophrenia, Alzheimer’s disease, or ADHD. In contrast, chronic tobacco smoking has been shown to be associated with deficits in cognitive function, prominently verbal memory, and processing speed, in middle-aged to elderly adults.

“Structural alterations, including decreases in grey matter volume of various brain structures and increased fractional anisotropy in diffusion tensor imaging studies, have been found not only in older smokers but also in smokers younger than 30 years of age,” Baska explained.

“Overall, there is now substantial evidence that tobacco smoking is associated with changes in brain structure and neural circuitry in brain regions and systems clearly implicated in many psychiatric disorders. These findings, together with the high prevalence of smoking in psychiatric populations, highlight the importance of including smoking as a potential confounding variable in studies examining neural mechanisms of psychiatric disorders,” Baska notes.

Smoking as a modulator of the effects of psychotropic medications

Smoking/nicotine may modulate the metabolism of other psychoactive agents. The effects of smoking status on the metabolism of psychoactive drugs may be an additional way in which smoking could influence measures of brain function in some psychiatric populations.