As cannabis use increases, physicians need to be familiar with the effects of both cannabis and tobacco on the lungs. However, there have been very few long-term studies of cannabis smoking, mostly due to legality issues and the confounding effects of tobacco. It was previously thought that cannabis and tobacco had similar long-term effects as both cause chronic bronchitis. However, recent large studies have shown that, instead of reducing forced expiratory volume in 1 s and forced vital capacity (FVC), marijuana smoking is associated with increased FVC. The cause of this is unclear, but acute bronchodilator and anti-inflammatory effects of cannabis may be relevant. Bullous lung disease, barotrauma and cannabis smoking have been recognised in case reports and small series. More work is needed to address the effects of cannabis on lung function, imaging and histological changes.

The vestibular system sub-serves a number of reflex and perceptual functions, comprising the peripheral apparatus, the vestibular nerve, the brainstem and cerebellar processing circuits, the thalamic relays, and the vestibular cerebral cortical network. This system provides signals of self-motion, important for gaze and postural control, and signals of traveled distance, for spatial orientation, especially in the dark. Current evidence suggests that certain aspects of this multi-faceted system may deteriorate with age and sometimes with severe consequences, such as falls. Often the deterioration in vestibular functioning relates to how the signal is processed by brain circuits rather than an impairment in the sensory transduction process. We review current data concerning age-related changes in the vestibular system, and how this may be important for clinicians dealing with balance disorders.

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Increasing cannabis use and legalisation highlights the paucity of data we have on the safety of cannabis smoking for respiratory health. Unfortunately, concurrent use of tobacco among marijuana smokers makes it difficult to untangle individual effect of marijuana smoking. Chronic cannabis only smoking has been shown in large cohort studies to reduce forced expiratory volume in 1 s/forced vital capacity via increasing forced vital capacity in chronic use contrary to the picture seen in tobacco smoking. The cause of this is unclear and there are various proposed mechanisms including respiratory muscle training secondary to method of inhalation and acute anti-inflammatory effect and bronchodilation of cannabis on the airways. While cannabis smoke has been shown to increase symptoms of chronic bronchitis, it has not been definitively shown to be associated with shortness of breath or irreversible airway changes. The evidence surrounding the development of lung cancer is less clear; however, preliminary evidence does not suggest association. Bullous lung disease associated with marijuana use has long been observed in clinical practice but published evidence is limited to a total of 57 published cases and only one cross-sectional study looking at radiological changes among chronic users which did not report any increase in macroscopic emphysema. More studies are required to elucidate these missing points to further guide risk stratification, clinical diagnosis and management.Key pointsCannabis smoking has increased and is likely to increase further with relaxation of legalisation and medicinal use of cannabinoids.Chronic marijuana smoking often produces symptoms similar to those of chronic tobacco smoking such as cough, sputum production, shortness of breath and wheeze.Cessation of marijuana smoking is associated with a reduction in respiratory symptoms and no increased risk of chronic bronchitis.Spirometry changes seen in chronic marijuana smokers appear to differ from those in chronic tobacco smokers. In chronic marijuana smokers there is an increase in FVC as opposed to a definite decrease in FEV1.Multiple case series have demonstrated peripheral bullae in marijuana smokers, but no observational studies have elucidated the risk.There is currently no clear association between cannabis smoking and lung cancer, although the research is currently limited.Educational aimsTo update readers on legalisation of recreational and medicinal cannabis.To summarise the evidence base surrounding the respiratory effects of inhaled marijuana use.To provide clinicians with an understanding of the main differences between cannabis and tobacco to be able to apply this to patient education.To highlight common respiratory problems among cannabis users and the need for recreational drug history taking.

BackgroundWith increasing cannabis use, physicians need to know more about its respiratory effects. However, there are few long term studies of cannabis smoking, mostly due to legality issues and the confounding effects of tobacco.AimsWe reviewed the effect of chronic cannabis use on bullous lung disease.Methods18 out of 69 English-language publications, prior to April 2016, from MEDLINE, Scopus, and Web of Science databases, which reported bullous lung disease in cannabis users, were examined. Case reports and case series were included.ResultsThe only cross-sectional study reported an increase in the rates of macroscopic emphysema in tobacco only (17 of 92) and tobacco + cannabis smokers (15 of 91), but not in cannabis only smokers (1 of 75) compared to non-smokers.1The remaining case series and case reports described a total of 56 marijuana smokers presenting with bullous lung disease, often with pneumothorax and predominantly upper lobe involvement (Table 1). Concurrent tobacco smoking was present in all but 3 cases. The majority of cases reported heavy cannabis use, though direct comparison was difficult due to variation in usage measurements. All 4 case series that measured lung function reported normal findings.ConclusionsWhile the clinical association of cannabis smoking and peripheral lung bullae is well recognised (and consequently often not reported) there is scant documentation in the literature correlating marijuana smoking with bullous lung disease.ReferenceAldington S, et al. Effect of cannabis on pulmonary structure, function and symptoms. Thorax. 2007;62(12):1058–63.Abstract S127 Table 1Summary of case studies and case series associating cannabis smoking and bullous lung disease