Recent Findings in Marijuana Smokers

 Published: December 29, 2022

By: Mary Martinasek, PhD, CPH, MCHES, RRT


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Clinical paper reflection of the article “Chest CT Findings in Marijuana Smokers” published in Radiology Journal 2022. 

This review will provide an overview of the study design, the effects of marijuana on the lungs, a summary of the results, and considerations for respiratory therapists.

Study Design

Many research study designs help facilitate data collection and analysis and answer a researcher’s questions. Study designs are often based on time, meaning that some studies collect data over time (prospective), others collect at one point in time (cross-sectional), and some, like this study, look back in time (retrospective). This particular study was a retrospective case-control study focusing on CT lung changes in three groups of patients who had CT scans conducted prior to 2020. The retrospective part of the study looks at previously completed CT scans. The case control represents multiple group comparisons, usually with a control not affected by an intervention or behavior. This study compared three groups, including marijuana smokers, tobacco-only smokers, and nonsmokers (control). The study subjects considered were the marijuana smokers and the tobacco smokers, and the controls were those who reported never smoking. Two thoracic fellowship-trained radiologists reviewed all CT images. The radiologists had no prior history of the patients; therefore, they were blinded in their reviews of the CT scans, helping to avoid bias in their CT scan assessments. Their assessment of the CTs focused on emphysema and airway changes (bronchiectasis, mucoid impaction, and bronchial wall thickening). The two radiologists conducted interrater reliability measures on their readings of the CT scans. This is important because when multiple researchers are involved in studies that are evaluated individually, the goal is high reliability, meaning that their assessments/readings are similar or in close agreement. For bronchiectasis, their scores were low; for bronchial wall thickness, their scores were moderate; for emphysema and mucoid impaction, their scores were high. Therefore, the reliability scores suggest that their readings of the CTs are most reliable for diagnosing emphysema and mucoid impaction.

Effects of marijuana smoke

Tobacco smoking’s effects on the lungs are well documented. Regarding marijuana, what is known is that marijuana smoke contains many compounds that are carcinogenic and affect the respiratory epithelium; however, due to the substance being illegal for decades, there has been very little research conducted. From a clinical point of view, Delta 9 THC has known benefits for specific patients, such as pain control for multiple sclerosis, nausea control, and appetite promotor for chemotherapy patients. However, Delta 9 THC is not devoid of cognitive and respiratory effects that may overshadow the unwarranted optimism regarding the benefits. Our respiratory tract is delicate, and exposure to noxious chemicals of any kind can exacerbate existing airway diseases such as asthma and damage the epithelial barrier resulting in inflammation, chronic lung disease, and infections.

Summary of the results

Prior to discussing the results of this study, it should be noted that one evident limitation of this study is that 50 of the 56 marijuana smokers also smoked tobacco. Therefore, the findings cannot be attributed solely to the use of inhalational marijuana. Regardless, the results highlight that the compounded effects of marijuana and tobacco produce additional adverse effects on those who exclusively were tobacco smokers. The study highlights their overall findings between the groups. It also highlights their findings when they matched by age between the groups. In particular, the CT scans indicated greater paraseptal emphysema in the age-matched patients. Pulmonary emphysema is typically categorized as centrilobular, paraseptal, and panlobular. Centrilobular emphysema is the most commonly seen with a long history of tobacco smoking. Panlobular is emphysema we often see with alpha-1 antitrypsin deficiency. Paraseptal emphysema (also known as distal acinar emphysema) affects the distal alveoli’s ducts and sacs.

Interestingly, if it occurs alone, it may not cause any respiratory symptoms and can be unrecognized clinically. However, it may result in spontaneous pneumothorax, particularly in young adults. One risk factor for paraseptal emphysema is a history of smoking tobacco. The findings also were significant for overall emphysema (paraseptal and centrilobar) in the marijuana smokers. Additionally, both bronchial thickening and bronchiectasis were noted as greater in the marijuana smokers as compared to the tobacco-only smokers. Most concerning is the younger aged marijuana smokers, who have less lifetime exposure, exhibited cumulative negative effects on the lungs. Regarding nonsmokers, this is the best scenario. Whether a marijuana smoker or a tobacco smoker, your lung health is worse than someone who has never smoked.

Considerations for Respiratory Therapists

Most hospitals have an intake form that asks about smoking history. What is not asked on this form is elicit behaviors such as marijuana smoking. When counseling patients in the hospital, it is important to start with the 5 As. These include Ask, Advise, Assess, Assist, and Arrange. Ask the patient about their smoking status, both tobacco and marijuana. Understanding duration and amount are also helpful in gaining a sense of history. Record this information in the patient chart. For Advise, this is an opportunity for you, a respected health care provider, to advise the patient to quit smoking. Assessing their readiness to quit will let you know whether or not to proceed to the assist stage of either suggesting to the prescribing doctor a pharmacologic agent or over-the-counter nicotine replacement therapy. As an RT, you can counsel the patient on how to quit using motivational interviewing skills or refer the patient to a quit coach or department that provides smoking cessation.

Having more knowledge about the effects of marijuana on the lungs allows you to educate the patient on the ill effects of inhalational marijuana on the lungs. Likely most people who smoke do not believe it is harmful and do not feel a sense of addiction. There are smoking cessation counseling billing codes that can be used, such as codes 99406 and 99407, in particular. Medicare covers two cessation attempts per 12-month period. Each attempt includes a maximum of up to 4 intermediate (i.e., less than 10 minutes (99406)) or intensive (i.e., greater than 10 minutes (99407)) counseling sessions, with a total Medicare benefit of 8 sessions per year. As an RT, you could suggest to the doctor to prescribe simple spirometry to assess the patient’s FEV1, which may help to indicate the early stages of emphysema.

Additionally, low-dose CT scans are being used across the US to diagnose early lung cancer and potentially save a person’s life. Saved by the Scan is a program that can help. For information and eligibility details, visit HERE.

In summary, this article highlights the combined negative effects of marijuana and tobacco on the lungs and provides information to use as talking points when educating your patients.

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